Changed image caching to use weak tables

1. Much cleaner code than the old reference counting system.
Updated Drawable to match new image behavior
Removed all drawing related code from map

1. From here on out, will enforce separation of data and presentation.
Removed old reference to freeing images in scene
Updated MainMenu to new image names

1. No longer require extensions, intended to be a straight name or ID.
Further added to default scene behavior
Better scene exit behavior
Better organization of the scene source file
Updated Instructions to the new scenes behavior
Removed drawing related code from pawns
Updated State to new Pawn behavior
Updated last two scenes to new Scene behavior