Minor fixes to returning references to locals in various places.

Adds tet-tri map and all the support functionality that it needs

Adds Tetra-Triangular mesh map.
TODO: Code check and add tests

(1) `SimulationManager::startSimulation()` will check if a Viewer is
already rendering, and will only start a rendering/interaction loop
in the main thread if it isn't. This allows us to work with two
possible cases:
(a) a QT Application with an existing widget for rendering, in which
case we do not want to control the rendering window ourself in a loop
(b) a standalone `vtkRenderWindow` application, in which case we do
want to create a window when our simulation starts and loop until the
window is closed.

(2) `SimulationManager::startSimulation()` can be launched with a debug
boolean option (off by default), which will allow to not automatically
simulate the dynamics of the scene, to be able to interact with the
scene beforehand (using the mouse).

(3) `imstk::InteractorStyle` is based on vtkInteractorStyle specifically
the trackballCamera and allows to ignore mouse events in simulation mode,
and uses key events to control the simulation:
's' : start simulation
'e' : end simulation
' ' (space) : pause/run simulation

(4) The `Viewer` class and the `InteractorStyle` class have been moved
to the `SimulationManager` module, since they are more drivers of the
application themselves.

(5) The 'Sandbox' example has been refactored to make it easier to test
autonomous tests, and updated to use the new driver architecture brought
with this commit.

- SIMULATION adds the object actors and set the
interactor style to no interactions.
- DEBUG adds additional actors to visualize
lights, the camera, axis, and set the interactor
style to trackball to interact with the scene.

Light still a WIP

Adds visual tests for Isometric mapping

Changes names of math constants

Uses imstk defined math constants

Adds geometry map base class and isometriMap

Signed-off-by: Sreekanth Arikatla <sreekanth.arikatla@kitware.com>

Can directly used to create visual objects.

Also use unordered_map in SimulationManager.

Was not applying the quaternion on the good side.

Uses a dummy implementation of imstkScene to test
a module execution in multithreading.

form each UnitTest directory to avoid warning C4138 in windows.

in order to facilitate the creation of device servers and clients.

componenents.

Use configuration path for examples in order to locate
configurations files.

Modify AVMNidus, FEMSimulator and Shaders examples.

Small fixes all over the place.

- This calls `VTKRenderer::setRenderWindow`. Needed to use a
vtkRenderWindow from another instance (example : for a QT
application, use QVTKWidget renderwindow)
- Rename `VTKViewer::getRenderWindow` to `getVtkRenderWindow`
- Use internal functions in `getVtkCamera` and `getVtkRenderer`

Allows for the following workflow :
1) Create a `VRPNDeviceClient` by specifying its URL (name@ipadress)
and its type (see `DeviceType` class). The subclass `VRPNForceDevice`
is setting the style to `PHANTOM_OMNI` by default for now.
2) Create a `VRPNDeviceServer`
3) Call `VRPNDeviceServer::addDeviceClient()` to add the client created
on step 1). This will analyse the IP, name, and type of the device
client to instantiate a VRPN device connection. The added devices are
then stored in three `std:map` so the `mainloop()` can be called during
the execution.

Updated their use in `FEMSimulator` and `LaparoscopicCamera` examples.

Many are formating changes and others are
bug fixes as well as some refactoring.

from SimMedTK to iMSTK.

Modify the license notice in each file.
Add LICENSE file.

from SimMedTK to iMSTK.

Modify the license notice in each file.
Add LICENSE file.

by examples and unit tests.

Revert some changes and make it build, run FEMSimulator example

CollisionContext/CMakeLists.txt was contributed by Sreekanth.

iMSTK time stepping method.

classes.