host of changes to accommodate Atlas:

• input.cpp allows feeding in events from the outside (will be used by main.cpp and Atlas msg loop)
• most of main.cpp split into ps/GameSetup.*
• main.cpp is now a "controller" that drives the game via SDL events (Atlas is another such controller that can override main.cpp). it calls GameSetup functions to set up and processes messages.
• add functions to import AtlasUI.dll automatically

also, the usual refactoring ;)