Fix listenbrainz track length submission and include submission client details

[phw]

This fixes the track length submission for ListenBrainz. ListenBrainz defines the fields duration and duration_ms for this, see https://listenbrainz.readthedocs.io/en/latest/users/json.html . Without this information LB will not show a track length. It might also prematurely remove the "now playing" notification for longer tracks.

As I understand from the code the track length is in seconds precision, hence the duration field is being used. duration_ms would be for milliseconds.

This PR also includes the fields submission_client as defined in the LB API docs linked above.

[sentriz]

thanks!