extracted the IMediaModel interface and the MediaModel class
added the Playlist and PlaylistEntry classes
added the ability to load a list of existing playlists from subsonic
added the ManagePlaylist ViewModel/View and implemented its population
added the GetPlaylistResult class and modified the ManagePlaylistViewModel to use it and load remote playlists
added the ability to load remote  playlist items
removed redundant code from playlist item
updated some subsonic results which did not dispose xml readers
Merge pull request #54 from cristi-badila/addSupportForPlaylists

Add support for playlists
fixed some serialization issues regarding PlaylisteEntries and Songs and added some missing specs
fixed an issue with serializing/deserializing ojects which inherit from MediaModelBase
fixed failing spec
removed duplicate event subscription
removed duplicate code The navigation service was set in both a property and a field
added some checks to fix some possible crashes with no descriptive error information
added the DeletePlaylist result
minor code refactoring
modified the way the bottom bar view model is set for collection view models
added the playlist bottombar viewmodel and added the delete functionality to the ManagePlaylistsViewModel
added the SavePlaylistViewModel and implemented saving new playlists