Rewrite tvrage search parsing using lxml instead of xmltodict. It is way
faster and simpler (150% to 1500% speedup on my rig, ~250% average).
It should result the same result as the xmltodict implementation,
however at this time both implementation are tried against the tvrage
xml result, then results are compared. This way we'll make sure that the
lxml implementation is as accurate as xmltodict.

Also, added new simple test to try to search again all show releases in
the db, even if already attempted.