* plugin: basic from_mp4 implementation
This patch introduces a very basic implementation of from_mp4, with only
a few bits of meta-data available. The rest of the available meta-data
(which is more than half left), will be included in a later patch
* Mp4: Almost all track metadata is implemented
Only meta-data that is not implemented is duration, facing some weird
issue I am going to check on later
* Mp4: All meta-data fields implemented
All meta-data fields that can be retrieved are now retrieved, with the
exception of duration for both tracks and the entire file itself because
there is still an issue. However, that will be fixed in the upcoming
patches
* fix: UntaggedValue::duration() serializes correctly now
Previous to this patch, there was an issue where when you would use
UntaggedValue::duration() it would result in an invalid JSONRPC
resulting string when using the protocol. This patch fixes this issue
* Mp4: Duration fixed for file and tracks
* plugins: Add plugin extra to src/plugins
* Mp4: Replace unwrap() with expect()
* Fix: Remove test mp4 file
