Adds GUI Skeleton
We now have PlayerGUI.cs as the script to control the gui, and Player.cs is now set up to hold a reference to it.
Player now also holds a reference directly to the camera, rather than the camera's transform, so that we can access its viewport rect.
Split Screen GUI
The GUI is now set up so that it can render correctly with the split screen setup.
Proper Split Screen GUI
MAN THAT WAS A HUGE PAIN IN THE ASS.
Unity's screen coordinates are all contradictory and shit, so getting the layout coordinates set correctly so that they would work with both split screen and single player was a pain.