Added SFGUI
Made sure SFGUI is displayed on the window
Made sure states are reset when frame ends

This was to solve a problem with SFGUI that resulted in nothing being
shown.
Support to pass an event down the stack
Support to pass render execution down the stack
Added a access function for the stack trough subclasses of state
Added function to easily check if state is on top
Enforced code style to State.*
Added so we can clear a sate stack easily
Added skeleton state for EditState