Option to prefer single episode releases over season releases:

- Added option "prefer_episode_releases" to config.ini. If a complete season of a show is added to the backlog this option will make sickbeard prefer single episode releases for that season over a comlete season release. I.e. if the complete season 1 of the show "Tv Show" is requested sickbeard will prefer "Tv.Show.S01E01...", "Tv.Show.S01E02...", over "Tv.Show.S01...". If not all episodes are available as singles the missing episodes will be picked individually from the season release (only supported for newznab providers). "Proper"/"Repack" from season release will be preferred over non-"Proper"/"Repack" singles (newznab).
- Changed logic in "pickBestResult" so that if the current "bestResult" already is a "Proper"/"Repack" it will not be overridden by another "Proper"/"Repack" further down the list. This also ensures that "Proper"/"Repack" single episodes always will be preferred over "Proper"/"Repack" season releases (if the "prefer_episode_releases" option is activated).