Delete components after post-processing

[stickell]

When I download a 1080p Youtube video using:

youtube-dl -f 137+140 youtubeid

I get 3 files, the m4a only audio file (stream 140), the mp4 only video file (stream 137) and the merged mp4 file.
Would be nice to add an option (something like --delete-commponents) that deletes the audio/video only components after the post-processing.

[jaimeMF]

Duplicate of #2108. Once we fix it, they will be deleted by default and kept with the --keep-video option.