[videomega] Add new extractor. Closes #3775
[videomega] Simplify (#3786)

* Use raw strings (r'foo') for regular expressions (enables highlighting and avoids some errors).
* title is always true-ish
[soundcloud] Support api urls with secret_token, Closes #3707
[soundcloud] Secret playlists and sets

Closes #3707 again.

No test cases because I don't know what urls to use that won't be turned
into public eventually (as it happened with the first one in that
ticket)
[drtuber] Fix categories
[ign] Fix extraction
[1up.com] Urls end now with '.html'