Playlist: Add Total Play Time and Expected End Time

Please add a summarization of all the play times in the playlist. The playtime of the single items is already there but a total (=summary of playtime of all items) would be greatly appreciated.

I this context it would be cool to also see the actual expected total time on the clock after all the items would have been played when starting at that moment.

This way it would make it much easier to compose a playlist given to someone's available time slots.