Remove 'Streams' page

[jcass77]

Tracks on the 'Streams' page now form part of the 'Musicbox Favourites' playlist, making a dedicated page for this unnecessary.

This issue is dependent on getting a few missing playlist features in place as described in #164, specifically the ability to add and remove tracks from a playlist.

[oouuppss]

Should be good to have a way to sort favourites/stream/playlist in some way too instead than having them all in one list.