Better Controller Support

Just pushed:

• A second button used for "cancel" (No game-play use - still a single button game) 
  • allows you to pause and quit the game
  • back out of all menus
  • you don;t have to press escape anymore! (but you still can)
• Mouse controlled player craft can now fire/thrust with the spacebar OR the mousebutton
• Hopefully fixed issues with mouse cursor being invisible for some of the people some of the time.
• Stress free mode no longer crashes on wave 3!