Bandcamp - check for various artists by checking if each track has a dash

I find it annoying when scrobbling compilations from Bandcamp (which don't set the artist to Various or Various Artists) that the track title contains the artist. I've made a modification to the scrobbler to work out artist from the track if either:

 - The artist is set to 'Various' or 'Various Artists' and track has a dash 
 - This is an album and all the tracks have a dash
		 
__Examples:__

- https://nothingbuthopeandpassion.bandcamp.com/album/nothing-but-nordic-music
- https://section27.bandcamp.com/album/s27-127-sectioned-v40

~~I guess the fact that the Bandcamp scrobbler for every time the duration updates has to work out the artist/track isn't the most effective mechanism and perhaps could be improved in another way.~~

__Done:__ Now listens to the `playing` event from the `audio` player.