Initial Matrix4/Vector4 classes
Make Matrix4 abstract to fix compile issues on some platforms, update sample to use Matrix4
Set window size
Frame time fix
Tenative support for flags when loading images
BYTES_PER_ELEMENT should be static
Inline
Improve frame timing
Merge branch 'next' into load-image

Conflicts:
	project/src/ExternalInterface.cpp
	project/src/backend/sdl/SDLApplication.cpp
	project/src/backend/sdl/SDLRenderer.cpp
	project/src/backend/sdl/SDLWindow.cpp
	templates/haxe/DefaultAssetLibrary.hx