Refactored from PBD pipeline

Mesh class is renamed to PointSet since
the word 'mesh' implies that connectivity
information is part of the class which is
not the case

Adds a sphere to mesh collision detection.
The radius of the sphere is small to use for picking.

/*=========================================================================

   Library: iMSTK

   Copyright (c) Kitware, Inc. & Center for Modeling, Simulation,
   & Imaging in Medicine, Rensselaer Polytechnic Institute.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0.txt

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

=========================================================================*/

 Add collision Mesh to sphere and plane coll. detection classes based on brute force approach.

1) Change the interactionPair structure to save
only one collisiondata per structure, and inform
the collisionhandling of a "side" defining which
object it is handling, therefore which way it needs
to read the collisionData

2) Update MeshToMeshCD to properly populate data
based on 1.

To geometries, objects, collision data

Still need to connect callbacks to retrieve collision data.

Adds time integrator which only sets rules for finite difference in time.
Adds comments for DeformableObject class

1) Clean up print methods
2) Put initialize, print, clear, getVolume on top
3) Add missing overrides
4) Replace extractSurfaceMesh by computeAttachedSurfaceMesh
5) Define Mesh::print
6) Use Mesh::clear in subclasses

Adds a function to check if a geometry is a mesh.
Adds printing to geometry class
Stylistic changes in extract mesh class

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

Use config based on https://gist.github.com/mkroman/1372117

Also remove headers in cmake files

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

Adding project name (iMSTK)

Skeleton of CMake architecture and of first few classes.