Torrent indexer refactor

@markus101 @kayone 
PURELY for review and discussion purposes.

The torrent-indexer-base includes torrents AND indexer-refactor.
The torrent-indexer-refactor is everything we changed on top of that to make it work.
This PR is between those two branches so we can use a PR to process feedback solely on those changes so we don't have to bother with unrelated code.

I'll leave comments here and there to explain what I did, and where I still have problems with. Once we decide how it should be I'll simply cherry-pick the appropriate code for indexer-refactor.

I wanted to talk about this, because I didn't clarify earlier.
I think adding these configuration properties to the RssParser allows it to be flexible and reused for various indexers without having to create derived Parsers for those indexers.
Do you guys agree with this idea? I'm not sure if the propertynames are clear enough, might need a comment.