Implement find_playlist_by_reference_id

[paltman]

Implemented the Playlist object and all the supported lookup methods

• find_playlist_by_id : Closed by dad1519e62ff166d869b9558fb3d1819eb04e8f6
• find_playlist_by_ids : Closed by dad1519e62ff166d869b9558fb3d1819eb04e8f6
• find_all_playlists : Closed by dad1519e62ff166d869b9558fb3d1819eb04e8f6
• find_playlist_by_reference_id : Closed by dad1519e62ff166d869b9558fb3d1819eb04e8f6
• find_playlists_by_reference_ids : Closed by dad1519e62ff166d869b9558fb3d1819eb04e8f6
• find_playlists_for_player_id : Closed by dad1519e62ff166d869b9558fb3d1819eb04e8f6