feat(lastfm): Add option to only send primary artist to Last.fm

[Whhoesj]

Last.fm doesn't support multiple artists per track. Add an option for the Last.fm config to send over only the primary artist of a track instead of all artists combined in a single string.

Issue: #81

[FoxxMD]

Thanks for the catching this oversight!

I can't think of a good reason anyone would want to continue concatenating multiple artists together since its not what LFM expects anyways so:

• please remove the onlyScrobblePrimaryArtist option so the LastFmScrobbler always uses first artist
• please rebase this to merge to FoxxMD:develop

[Whhoesj]

Change is in. It now always sends the primary artist. No options.