searcher filtering changes (please review)

- Filtering of Lossless min/max, Preferred bitrate % and already
downloaded check stops the searcher moving on to torrents if prefer NZB
set (and vice versa). Moved from sort_search_results to new routine

- Preferred bitrate low/high calc not quite right, should be target
size + high %

- Please correct me here but I think this logic ‘elif
headphones.PREFERRED_QUALITY’ is True if Preferred Bitrate
(PREFERRED_QUALITY = 2) which means it will always get lossy and
lossless. Surprised that no one has complained about this. Anyway, what
this means is that the ‘Allow lossless if no good lossy match found’
option kind of works although it shouldn’t! Changed to explicitly state
PREFERRED_QUALITY == 1 and added a flag to allow_lossless which is set
if Preferred Bitrate and High Limit and Allow Lossless are all set

- removed unused bitrate from rutracker