Add Series Options

@kayone @Taloth

This adds the backend support to let us add series and let users choose which episodes to monitor automatically (instead of at a season level) and let them perform a backlog search for missing episodes after adding.

This requires us to listen for two events, the series being added and the disk scan completing. I do feel its a bit fragile right now, since it will do nothing if Sonarr is restarted, the other option is a database table to store it.

No UI or tests in this one, wanted to make sure you guys are good with the approach. Also its specific to this scenario, maybe we need to make it more generic later on, but I didn't want to deal with that unless we require it (I couldn't think of a reason why we would right now).
yeah, I'm thinking db table. where commands are queued and we have certain number of worked threads that could process them. this would allow us to prioritize items as well, or have fast lanes reserved threads and background threads. 

I'm getting excited :dancer: