Rename MainApplication to App

It makes sense to have a short name because it's used in so many places.
The name "MainApplication" isn't any more descriptive anyway.
Merge rename-mainapplication-to-app (#202) into master

Rename MainApplication to App

It makes sense to have a short name because it's used in so many places.
The name "MainApplication" isn't any more descriptive anyway.
Rename MainApplication to App
Merge remote-tracking branch 'origin/master' into offline-guides

Conflicts:
	App/src/com/dozuki/ifixit/App.java
	App/src/com/dozuki/ifixit/model/Image.java
	App/src/com/dozuki/ifixit/model/search/GuideSearchResult.java
	App/src/com/dozuki/ifixit/model/search/TopicSearchResult.java
	App/src/com/dozuki/ifixit/ui/BaseActivity.java
	App/src/com/dozuki/ifixit/ui/FavoritesActivity.java
	App/src/com/dozuki/ifixit/ui/GuideItemView.java
	App/src/com/dozuki/ifixit/ui/auth/LoginFragment.java
	App/src/com/dozuki/ifixit/ui/auth/RegisterFragment.java
	App/src/com/dozuki/ifixit/ui/gallery/MediaFragment.java
	App/src/com/dozuki/ifixit/ui/guide/StepEmbedFragment.java
	App/src/com/dozuki/ifixit/ui/guide/StepVideoFragment.java
	App/src/com/dozuki/ifixit/ui/guide/ThumbnailView.java
	App/src/com/dozuki/ifixit/ui/guide/create/ChooseBulletDialog.java
	App/src/com/dozuki/ifixit/ui/guide/create/StepReorderFragment.java
	App/src/com/dozuki/ifixit/ui/guide/view/FullImageViewActivity.java
	App/src/com/dozuki/ifixit/ui/guide/view/GuideViewActivity.java
	App/src/com/dozuki/ifixit/ui/guide/view/TeardownsActivity.java
	App/src/com/dozuki/ifixit/ui/topic_view/TopicViewFragment.java
	App/src/com/dozuki/ifixit/util/UrlImageGetter.java
	App/src/com/dozuki/ifixit/util/Utils.java
	App/src/com/dozuki/ifixit/util/api/Api.java