[youtube] Move playlist test to extractor
[youtube] Move more tests to Playlist IE, and simply suitable.
[prosiebensat1] Fix bitrate calculation
[prosiebensat1] Make upload_date optional

The site has a crazy incorrect date in German formatting, but the correct date is nowhere to be found.
[swrmediathek] Remove deleted video test case
[spiegel] Remove deleted video from test cases
[xhamster] Remove md5sums from tests

We're now checking that the file is sufficiently large by default, and they seem to reencode the videos from time to time.
[youtube] Correct description in test case
[youtube] Modernize
[options] Move all options to their own file