refactoring, more comments, .dimUp

refactored pretty much the whole file (insanj style guides), added some
UIWindow private methods, added DimLog DEBUG-only macro, renamed most
things to be Dim-specific, added dimUp property of DimListener to
intelligently alter opacity at activation, used fmin/max instead of
ifs, used autoreleasepool and got rid of springboard check
(-registerListener:forName: is springboard-only anyway), STILL can’t
stop overlay from stealing touches (maybe tomorrow)
attempt at DimWindow with _ignoresHitTest

added DimWindow UIWindow subclass with -(BOOL)_ignoresHitTest override,
and attempted using -hitTest, -pointInside, -makeKeyAndVisible, and
.windowLevel (no luck anywhere)
switched _ignoresHitTest value FTW!

perfect impl using original Dim idea and rpetrich’s _ignoresHitTest
recommendation (via UISoftwareDimmingWindow’s shenanigans)
:shipit:

I should stop :shipit:’ing so much
Merge pull request #1 from insanj/master

Merge @Insanj's code so it actually works well (huge thanks!)