feat(audio-quality): Add preferred audio bitrate to createConferenceIq
feat(audio-quality): Add preferred audio bitrate to createConferenceIq

Pass a value for Opus' maxaveragebitrate parameter to Jicofo
iff opusMaxAvgBitrate is set as configuration option.

damencho/lib-jitsi-meet,jitsi/lib-jitsi-meet,jitsi/lib-jitsi-meet