deleted: some Direct3D-dependent code (LPD3DXBASEMESH & LPD3DXMESH)
changed: some class names. Dropped C prefixes.
fixed: header inclusion paths.
updated: .gitignore
updated: EntityRenderManager
cleaned up: the source code
updated: log code
updated: log code
added: a haeder file which contains a convenience function(s) for creating generic shaders
updated: OpenGL texture resource classes