iOS: TimeShiftingViewController now functional (for percentage).
iOS: Added controls to the SplashViewController.

Related to issue #405 and issue #415.
iOS: MobileLibraryBrowser: Now loading album art in background.
MobileLibraryBrowserPresenter: Added action for loading album art. Will need to add an action for canceling fetching album art later.

Related to issue #405 and issue #408.