- Rect no longer inherits from SDL_Rect
- renamed vcmi functions that used SDL naming format
- moved all functions in SDL_Extensions file into CSDL_Ext namespace
- SDL_Rect is now used only by SDL_Extensions, all other code uses Rect
- added documentation comments for classes, members and methods
- added const specifier to methods where applicable
- renamed some methods with more clear name
- removed some commented-out or unused code