[metadata.tvdb.com] Retrieve # votes (RatingCount).

Not much to write here. It just reads the `RatingCount`[1][2] field and translates it to `votes`, both for TV shows and episodes.

Copy/pasted from the RegExp for "Rating".

[1] http://thetvdb.com/wiki/index.php?title=API:Base_Series_Record
[2] http://thetvdb.com/wiki/index.php?title=API:Base_Episode_Record