* rename steps to pipeline module
* move pipeline entrypoint to pipeline module
* rename steps test module to pipeline
* fix paths after renames
* move step protocol to pipeline
* create pipeline status enum
* use Protocol from typing extensions
* Fix linting
- store cue(in|out) as strings
- reraise when executable was not found
BREAKING CHANGE: The analyzer requires 'ffmpeg'. The 'silan' system dependency can be removed.