Add force update of Playlists (feature #23)

[humor4fun]

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MVC and shared/_layout updates to expose a page for forcing all Playlists to be updated.

[TheUltimateC0der]

Please have a look at the changes I made to #22 to see how exactly you use Actions in a Controller.

Currently you trigger the update job for all Playlists, and ask the user after that for permission to trigger them. That does not make any sense.