Support different output formats (new `save-` commands)

[Breakthrough]

We need to support more output formats, such as EDL, FCP XML, and more. This issue tracks implementation of various output formats in sub-issues.

References:

EDL reference: https://github.com/mpv-player/mpv/blob/master/DOCS/edl-mpv.rst Chapter formats: https://github.com/rigaya/NVEnc/blob/master/NVEncC_Options.en.md#--chapter-string https://gist.github.com/schtritoff/8e0105060cb07c118863867429473830 https://github.com/Mtillmann/chaptertool/issues/1