Bug 841760 - Lazyer Settings app - CSS Part
(cherry picked from commit 2f86aad75e00ffd578f8f5245fcde81af2ef516d)
Bug 841760 - Lazyer Settings - JS Part
(cherry picked from commit bb65b9c82bade667a07bc699bdbd5c80daa44df3)
Bug 841760 - Lazy load more things in the settings app. part 3. r=etienne
(cherry picked from commit ef60a5e50ef39c7fd15cb07dbdfaa1a23cd7d747)