UI overhaul, new cleaner class and event handling hierarchy, better focus implementation
Merge branch 'master' of https://github.com/heronarts/P2LX

Conflicts:
	src/heronarts/p2lx/ui/UI.java
	src/heronarts/p2lx/ui/UI2dContainer.java
	src/heronarts/p2lx/ui/UI3dContext.java
	src/heronarts/p2lx/ui/UILayer.java
	src/heronarts/p2lx/ui/UIObject.java
	src/heronarts/p2lx/ui/UITabFocus.java
	src/heronarts/p2lx/ui/UIWindow.java