New Mission type: Protect Base Core

Hello Fam! This update introduces:

New Mission Type - Protect the Base Core (appears later during the game) - thanks Hardwater for the idea!

Gamepad Support - Tested on a Logitech F710, but most gamepads should work hopefully, if not use a re-mapper or whatever it is you zany kids use these days.  This took surprisingly long to do, since it required going through all the aspects of the game to make sure it all worked.

Linux Support - now runs natively on Linux

Now, I know what you are going to say: “But.. where are the new hats!?” And to that I say, fear not - they are coming!