Rebasing #1155 and applying some fixes. Had to comment out the
`mpd_notify_muxer_listener_unittest` because it depends on
`MockMpdNotifier` from `mpd/base` which has not been ported yet. Can
bring this test back once that has been ported.
Related to #1047
---------
Co-authored-by: Carlos Bentzen <carlos.bentzen@bitmovin.com>
Co-authored-by: Joey Parrish <joeyparrish@google.com>
This also normalizes the structure of all submodule folders so that
there is a clear place to put configurations, outside the submodule
source, but limited in scope to that folder.
Issue #1047 (New build system)