(*) This is a big commit involving UNFINISHED WORK. All the following comments are related to the creation of a new file format (file extension: .prim) for managing primitives (mesh + materials + textures).

- Client .obj "primitive" files (camera.obj and directional_light.obj) have been replaced by new primitive files (camera.prim and directional_light.prim).
- Removed TexturizedMesh class.
- DrawablesManager's methods addMesh() and createMesh() have been replaced by new createMesh() methods which accept new Mesh*Data structs as arguments.
- MaterialsManager::createMaterial() methods have been replaced by new createMaterial() methods wich accept new MaterialInfo struct as an argument.
- Now ClientPrimitivesManager::instantiatePrimitive() public method makes use of PrimitiveFile::read() method for importing primitives.
- Some debug messages have been removed (some of them have been replaced by assertions).
- Added a new Material constructor accepting a MaterialInfo as an argument.
- Mesh constructors now make use of PrimitiveFile::read() method and/or Mesh*Data structs.
- Mesh initialization code have been splited into several small and, I hope, more readable methods.
- Old Mesh::loadFromOBJ() method has been removed.
- Some Mesh attributes related to mesh's vertex data have been replaced by MeshVertexData and MeshOpenGLData instances.
- MaterialCreationCommmand's interface works now with MaterialInfo instances.
- Added all the information related to a given material to MaterialCreationCommand class as attributes.
- Added fixes and missing code to OBJPrimitivesImporter class.