ios: Refactor browser code some.
ios: Add proper license header to all files.
ios: Disable cover-art views if UICollectionView is not available.
ios: Have the list_directory use objects to cache properties about the items. Quite a bit faster too.
ios: Some cover view improvements:
   Don't allocate new views when reusing a cell.
   If a file item doesn't have an attached image, its filename will be printed in the cell instead.
   Images maintain aspect ratio when scaled.