Unless option have to be passed using the command line, this is the
recommended approach to pass options. It avoids "command line length issues".

Adding of a step for the configuration of iMSTK with OpenHaptics

Contributor: Alexis Girault <alexis.girault@kitware.com>

Contributor: Alexis Girault <alexis.girault@kitware.com>

This will not mandate the users that checkout the code to set up ssh

Add audio testing examples in sandbox. Add resources to the data folder

A cmake option to enable audio is provided which is not enabled by default.
Only audio module of the SFML is build using the cmake options.

Switch to sjh/vrpn to allow for quick changes to the
Arduino vrpn server/client

This prevents linker errors in Windows from finding multiple
copies of the vrpn base classes.

Co-Authored-By: Alexis Girault <alexis.girault@kitware.com>

Expand the imstk_add_library cmake function by exposing the variables
H_FILES (headers) CPP_FILES (source) and SUBDIR_LIST (build interface
directories - the current source dir is always included).

If those values are not manually set, the previous behavior applies,
where all the files and directories in the root directory are used for
that target.

Used that new mechanism for the Rendering target to prepare for Vulkan
integration.

Download Data from Girder according to data key files contained in iMSTK/Data

This uses ExternalData.cmake (Requires CMake >= 2.8.11 release).

Add TEST: Add ExternalDataTest to verify downloaded files from Girder
* Be sure the data requiered for the test is not there (delete it)
* Add the imstk_add_data(${target} ${data_list}) function in CMakeList.txt
which calls ExternalData_expand_arguments().
* It downloads the data provided by the data_list (relative path from
iMSTK/Data)

Add DOC: Add documentation on ExternalData Management
* How to add data to iMSTK from Grider
* Update data
* Use data

Eigen git tag which was currently used (e81ac4502ebbfde43a1e1761b36853d3ead47c33)
can not be checked out anymore as of Sunday, January 29 2017 for unknown
reasons, causing all builds on the dashboard to fail:

http://my.cdash.org/index.php?project=iMSTK&date=2017-01-29

error:
```
fatal: reference is not a tree: e81ac4502ebbfde43a1e1761b36853d3ead47c33
```

The main bottleneck with real-time VTK rendering so far
appeared to be the normals computation. This commit addresses
that issue by making use of the latest normals computation
filter in VTK: vtkTriangleMeshPointNormals.

While this filter is much (5 to 16 times) faster than
vtkPolyDataNormals, it does not check for consistency in the
cell orientations that could cause inverted normals, which
is why the vtkPolyDataNormals is called once in the surfacemesh
renderdelegate to retrieve consistent cells for the input mesh.

See VTK merge request for more information :
vtk/vtk!2271

PS: That MR requires the latest commits from VTK master, which
does not include work made on texture wrap mode nor on multi
texture attributes yet:
- iMSTK/vtk@62a7ecd8
- iMSTK/vtk@ae373026

define "StdVectorOfxxx" for all eigen matrix structures
used in iMSTK within std::vector.

See http://eigen.tuxfamily.org/dox-devel/group__TopicStlContainers.html

Requires to update SCCD to commit 645508940
which also updates its vec3 structure.

googletest git repository was using the SSH protocol
instead of HTTPS, which requires users to add an
ssh_key on github.com.

We switch all those external projects to HTTPS protocol,
but keep the ones hosted by ourselves on gitlab.kitware.com
in SSH since we might be contributing back to those
during development.

With the superbuild architecture, the inner project
is not added as a subdirectory in the superbuild project,
but configured through ExternalProject_Add(). For this
reason, the CTestTestfile.cmake at the top level (superbuild
project) does not add the Innerbuild directory in which
there is another CTestTestfile.cmake referencing the tests
of the inner project.

This commit includes the file `imstkCTestAddInnerbuild.cmake.in`
which calls `subdirs()` on the Innerbuild directory. That file
is configured in the top-level build directory, and added as
the TEST_INCLUDE_FILE property to that directory. This will
include that file to the top-level CTestTestfile.cmake, which
will therefore be able to reach the CTestTestfile.cmake in the
Innerbuild directory when running ctest.

Use this commit to also only solve external dependencies
in the superbuild tree, no need to to it in the innerbuild tree.

By adding testing source files in the same directory
than the target source files, those first ones were
included in the target executables by mistake.

ctests would currently only be created for each test file,
but the GTEST_ADD_TESTS function[1] could allow to register
all gtests as independent tests.

[1] https://cmake.org/cmake/help/v3.0/module/FindGTest.html

However, that function would not allow the use of a driver
executable, since it would force the `gtest_filter` flag to
appear right after the executable name in the command, while
a driver executable would need the name of the test file
beforehand.

This commit introduces a custom version of GTEST_ADD_TESTS
where `extra_args` is called before the `gtest_filter` flag
to allow the use of an executable driver.

Note: as noted in the doc above[1], testing each gtest is
slow since they all necessite the startup of an executable.
The previous option of testing per file is therefore kept
but commented. A future focus of interest could be to
customize `add_test` to then run all gtests at once like
GoogleTest does by default.

Allows to create tests in iMSTK using google test and ctest.
Ctests are created by test files, and not by gtest functions.

Requirements:
- Requires a 'Testing' subdirectory with cpp files for each
  class to test.
- Google Test and Google Mock should be used to create unit
  tests, see the documentation below:
  https://github.com/google/googletest/blob/master/googletest/docs/Documentation.md
  https://github.com/google/googletest/blob/master/googlemock/docs/Documentation.md
- Test files should be constructed as described under\
  `imstk_add_test()` declaration

FindVRPN: The order in which the libraries were
found was creating an compilation error during
linking on Linux, as well as windows when being
read from an external project.

iMSTKConfig.cmake.in: ${PROJECT_NAME} would not be
set to "iMSTK" from an external project.

External_VRPN: VRPN_BUILD_SERVERS:BOOL was defined
twice in imstk_add_external_project(VRPN)

Fixes #66

Integrate the following commit:
iMSTK/VegaFEM-CMake@7bc1bda6

Also remove useless iMSTK_EXTERNAL_PROJECTS_PATHS
variable in External/CMakeLists.txt

Using a git branch name for an external project would
update the repository of that external project when
building iMSTK even though it would not be tested.

By hardcoding a certain commit #, we can make sure we
need to specifically update the external project git_tag
to update the external project.

This commit updates to the newer version of VegaFEM which
should resolve some errors:

iMSTK/VegaFEM-CMake@d1ab0858

On some windows systems, the command `cmake -E copy`
within `copy_ftd2xx_static_command` renames the ftd2xx.lib
file as `lib\${BUILD_TYPE}` instead of copying it within
the directory of the same name. Because of this, the directory
can not be created in the future for other libraries, explaining
the high number of compilation errors (~50)