Make porting to other platforms easier. Move platform specific files into their own /Platform subfolder.
Reduce use of CM_PLATFORM where possible
Split class into different files per-platform where possible

GLRenderer
 - Win32Window
 - Win32Prerequisites
 - Win32Context
 - Win32GLSupport
 - GLPRerequisities - different includes are added depending on platform 

Utility
 - Timer
 - DynLibManager (currently has everything in one file, need to split it up)
 - FileSystem - has some OS specific functionality

Core
 - Cursor - Also move to Utility?
 - WindowEventUtilities - Rename the class, also split it into separate files per platform
 - Application::loadPlugin - uses different extensions based on platform. Move platform specific functionality outside?

Search for all occurencess of CM_PLATFORM
 - Although in all other cases use of CM_PLATFORM can be removed, or is justified