* removed classes managed by CInstanceManager
except for CObject, CPyro, CBrain and CPhysics
because of dependencies
* refactored instance searching to use existing singleton instances of
CApplication, CEngine and CRobotMain and calling their getter
functions
- fixed model loading code
- added simple model viewer (model_test) in src/graphics/opengl/test
- added system time stamp code
- split the code in app/system modules to separate headers
- added debug messages in model loading
- minor fixes in OpenGL engine