Fixed Issue with Artists, added additional artists sections and changed premieres to recently added

Here is a fix of the MTV-Music-Videos channel. You had mentioned that the artist section wasn't working, so I gave it a look. They changed the URL for artist pulls, so I set up a pull that also allows pulls by genre, popular, emerging, etc. Also, premieres no longer works, so I changed it to the recently added block on the music videos home page.

Also see note at top in reference to Topspin videos. Which seems to be an additional video service (like Vevo) that is being used for new artists videos. For right now, I just tell the channel to ignore those videos since it is not supported and there are not that many artist who have Topspin videos.