Direct stream copy extractor and fix

Description

It is now possible to use a direct stream copy when extracting sub-movies with the new MediaCutter use_stream_copy parameter.
If set to True, input streams are directly copied instead of being decoded and re-encoded, which speeds up extraction a lot. If False, streams are decoded and re-encoded. Video streams are then re-encoded with a yuv420 format.

A small bug was fixed.

What's Changed

• 15426 fixes by @gplsteph in #64

Full Changelog: 1.1.10...1.1.11