Fix ffmpeg

[srounet]

FFmpeg usage was broken, this PR aim to fix the FFmpeg usage and address some utf-8 issues for movies with non-ascii characters.

Changes:

• Add Contributors file (with all existing contributors from master branch)
• Fix FFmpeg, mostly fixing argument naming. Now both HandBrake and FFmpeg are Harmonized.
• Handle issues with non-ascii filenames breaking ffmpeg (it is mostly a workaround), by renaming movie titles to ascii-ready filenames.

Those changes have been tester over a full iteration of 10 BR, both ripping and compressing files.

[JasonMillward]

Thank you very much for this