Set bitrate limits for transcoding (fixes #638) (#1135)

* Set bitrate limits for transcoding (fixes #638)

* added optimization script and test, changed stuff

* fix test, improve docs

* re-add optimize-old-videos script

* added documentation

* Don't optimize videos without valid UUID, or redundancy videos

* move getUUIDFromFilename

* fix tests?

* update torrent and file size, some more fixes/improvements

* use higher bitrate for high fps video, adjust bitrates

* add test video

* don't throw error if resolution is undefined

* generate test fixture on the fly

* use random noise video for bitrate test, add promise

* shorten test video to avoid timeout

* use existing function to optimize video

* various fixes

* increase test timeout

* limit test fixture size, add link

* test fixes

* add await

* more test fixes, add -b:v parameter

* replace ffmpeg wiki link

* fix ffmpeg params

* fix unit test

* add test fixture to .gitgnore

* add video transcoding fps model

* add missing file