Bug 1022971 - Rename Icon grid object to Mozapp

https://bugzilla.mozilla.org/show_bug.cgi?id=1022971
Dependency ordering without modules sucks. It's not terrible because we catch it if we break, but it is ugly. I also don't want to have to add exports.GaiaGrid = GaiaGrid || {} to ever file, but if you think that is better we can do it.