Setup for platform independence layer
Submodule setup
Moved OS class to platform module

+ cmake script modifications
Remove OS class from DBGL_Base
Fixed linux distribution check
Window interface
Added Input class
Removed unneccesary friend classes
Started to implement window
Added implementation handling
Added test project
Removed superfluous includes
Proper termination, swapbuffer, ...
Monitor
Implemented timer
Window cleanup
RenderContext implementation (WIP)
Render context for windows
readPixels(), enumerations
ClearColor and multisampling