add end-to-end test for compiled releases

All of our 0.1-releases and 0.2-pre-releases were unusable on at least one plattform (mostly linux, sometimes even all) because of packaging issues that did not appear during development. I think it might be a good idea to have some form of automatic testing that checks that at least the basic usage is possible with the build package.

This could include:

* Transcribing a document (with and without diarization)
* Deleting some words
* Re-arranging some words
* Exporting (Audio, Video, Subtitles, OTIO?)