Direct screenwavemedia.com URLs support (issue #3766)

The first patch adds support for direct downloading from screenwavemedia.com URLs (by modifying the cinemassacre extractor). The second adds teamfourstar.com support on top of it.

**Warning**: the patches were not tested very well, and probably should not be accepted without review; I feel the code is quite inefficient with its multiple URL parsing and may not cover some corner cases.
Why have three extractor classes instead of just three methods?

I thought it would be simpler. One thing (I think) it simplifies is extracting the metadata from the "embedding" site when given a "generic" SWM player URL, with graceful fallback to metadata extracted from the player page itself. With separate classes, I would have to muddle in other classes' internals, or instantiate them just to throw them away immediately, or whatever… well, maybe you can show me something more elegant.