New 0.x testing update

This update improves and adds a lot of features to DuME, especially an improved color management workflow.

All details are in the changelog: https://dume-docs.rainboxlab.org/changelog.html

Note for Linux users: Color management now needs some filters available only in FFmpeg > 4.0
If your distribution does not provide it, you should install the DuME-static version (.dev) or use the .AppImage. Both builds include a static version of ffmpeg 4.2 and should work on all systems.