submission: QMPlay2, yet another multimedia player

[RJVB (René Bertin)]

I've been trying out a Qt5-based multimedia player, QMPlay2 and after some back and forth with the nicely reactive author I think the time is right to submit my port for it.

Some advantages over VLC as I know it:

• works with FFmpeg 3.x
• easier and configurable interface with plenty of useful features like YouTube browsing (and downloading)
• a playlist that survives restarts
• single-frame stepping
• integrated support for hardware acceleration (VideoToolBox based, doesn't work on my system though (HD3000 GPU))
• builds out-of-the box or almost and uses CMake, as opposed to the significant hacking required of VLC's already messy autoconf-based build system.

Without hardware acceleration it burns a bit more CPU than VLC though, possibly because it uses Qt instead of a purely native backend.