Ends up adding/removing playlists from/to android/gs in-app/gs server

SoloPlaylistsActivity: Save/remove menus in onContextSelectedItem. When
removing a playlist from android DB, still show playlist in available ones.
When removed from the available list, playlist is removed from the server.
UnisonDB: Insertion/deletion from databases in atomic way
strings: Adds some error messages
FIX various bugs in playlists management