Partial fix for some issues with absolute episodes (those not in a season)

The documentation claims that we support episodes not in season folders, but they currently do not work at all. Such episodes are not recognised by the episode resolver, as the regexs for them were not used due to them being potentially confused with movies (they were also not very good).

I've updated those regular expressions to match against a few more naming formats, and also arranged them such that miss-identifications should cause more consistent and predictable errors. e.g. The series name could cause problems for every episode, but you won't get one odd episode miss-identified due to that episode's title.

The episode resolver only considers these regular expressions in unambigious situations. i.e. the media folder is of a TV Series type.

I also fixed an error in the tvdb provider which was preventing it from collecting any metadata for episodes with absolute numbers (which I think was probably a mistake I made).

These episodes are now identified correctly, but they still do not work. The episodes show up as children of the series in the library explorer when you are looking at the physical data (which is correct), but if you switch to one of the user views, the episode appears empty. I expect many of the clients also do not expect a series to have episodes as children instead of seasons.

Auto-organise and the missing/unaired provider probably also need a looking at for these.