iOS: Fixed bug in pushing dialog subviews (they didn't work the second time a screen had been created).

Related to issue #405.
iOS: MobileLibraryBrowserViewCtrl - Now flushing images when the view disappears. The images are reloaded once the view appears again. This optimizes memory usage.

Related to issue #405.
iOS: Fixed several bugs in the image resize routine. Now using the same routine for Mobile Library Browser and Player.
iOS: Centralized more UI colors into GlobalTheme.

Related to issue #405.