mmg portable: put jobs folder in mmg.exe's folder
tests: add cases for Opus in experimental mode
Refactoring
Opus: write DiscardPadding for last packet; read it when muxing from Matroska
Rakefile: task for cleaning just the unit tests
timecode_c: add samples()/to_samples() conversion
Opus: write seek-pre-roll header element
Opus: write codec delay header element
Tests: More Opus tests
Opus: output packets taking codec delay/seek pre-roll into account
Opus: drop /EXPERIMENTAL codec ID suffix
Translations: update German & list of translatables