Importer: Full-screen viewing, UI refinement, refactoring

Bug: 7990333
Bug: 8151814
Bug: 8037411

This CL adds or changes the following things:
 - Full-screen image viewing and UI for switching modes
 - Moved general functionality from MtpThumbnailTileView
   to MtpImageView to allow for reuse in full-screen image
   use-case
 - MtpBitmapCache moved from ui to data package
 - Orientation now respected when set in image metadata
 - Miscellaneous UI consistency issues fixed
 - Miscellaneous instability issues fixed

Change-Id: I5f188b763617b693e32fedc03273d711d604922a
18 files changed