Track texture mapping
Fix track mapping and sphere particle position
Flare textures should work now
Ground spot texture drawing
Transparent plant textures
ComputeSphereVisibility and fixes in CEngine TODOs

- view frustum culling with ComputeSphereVisibility - game should run
  faster now
- resolved/removed most TODOs from CEngine
- fixed OpenGL tests
Main loop enhancement

Frame updates were posted one frame behind in event queue
Performance counters
Fixed syntax error in Blender script
Static objects using OpenGL VBOs and display lists
Emit info message for GTest source.
Use system GMock and GTest if they are available

- Drop library addition to upstream GTest.
- Fallback to convenience copy if the system libraries are not installed.
Merge pull request #88 from OdyX/dev-graphics-system-gtools

Use system-provided Google tools in dev-graphics
Revert "Merge pull request #88 from OdyX/dev-graphics-system-gtools"

This reverts commit f5b4705cad6c7071a24912b81987a488a8cef0f7, reversing
changes made to 4811defca2eeea69e40346be6b1647f276db8c76.
Engine optimization - rewritten model management

 - new class CModelManager
 - rewritten engine object structure in CEngine
 - created shared model data instead of separate objects per each
   model instance
 - minor refactoring
Fixes and refactoring
Fixed spider and worm model loading
In levels' lists, fallback to english

- Implemented in a naive way: Take the English version if found, but
  continue until the translated version is found. This has the drawback
  of letting the loop reach its end if the level has no translation.
Let CMake rely on data's CMakeLists.txt if it exists

- Also update data to latest 'dev', where the CMakeLists exists
Add categories to Desktop Entry file

As per the "Desktop Menu Specification" 1.0, especially Appendix A.