Omit Mac hidden files from repo

Who needs .DS_Store anyway?
Generated Javadoc
Eclipse for Mac faffing

I needed a different Java library for some reason. Don't want to break
your own versions.
Made EvaluationStack .equals comparable
Abstract Challenge class

Abstract class is the most general representation, also includes a
simpler, more practical subclass.
ApplicationFrame for UI
Coded up some Modes n shit

And a bangin manager fo' tha modes
Tidied up Mode structure

Matches Google Doc explanation, Improved ModeManager
UI for the Store

No frills. Will be tested when some other components come together.