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)