Current implementation:
+----------------------------------------------------------+
| BaseItem <-| FileItem <-- URLItem <-- URLFromPlaylistItem|
| <-| RadioItem |
+----------------------------------------------------------+
^
|
v
+--------------------+
|PlayList |
|PlaylistItemWrapper |
+--------------------+
Goal:
+----------------------------------------------------------+
| <-| URLItem <-- URLFromPlaylistItem |
| BaseItem <-| FileItem |
| <-| RadioItem |
++---------------------------------------------------------+
^
|
v
+-----------+
|PlayList |
| |
+-----------+