Hooker: corrected render positioning.
Camera: added screen-relative position getters.
Added Screen class & system; added MainScreen module.

Core:
	moved Core-specific data into local data var;
	corrected Camera.init() call (was not updated to new signature);
	moved all demo stuff to MainScreen module.

State: enable gfx_debug by default.
Added ST2 project file and .gitignore.