Initial implementation of .obj file shape loader

- Also added several new models in .obj format:
  - the suzanne model exported from blender
  - an icosasphere
  - a unit cube
Multiple changes

- Added a new simple example showing the usage of the ObjMesh loader.
- Minor updates of tools.
Update of the build system and tools

- Added instructions for building of .obj models.
- Added dependencies of examples on obj models.
- Minor updates in doxyfile.
Merge branch 'develop' into feature-obj-loader
Update of the ObjMesh loader

- Added loading of material numbers and names.
- Added loading of tangent vectors.