have the AudioMixer handle silent audio, send silence from Interface when gate closed
fixes to silent audio frame sending
some potential fixes to QByteArray crash
have agent optionally send silent stream flag
repair _clientSamples copying into _clientMix
Merge branch 'master' of https://github.com/highfidelity/hifi into audio-scaling
resolve conflicts on merge with upstream master
cleanup writing of silent frame to ring buffer
Merge pull request #2350 from birarda/audio-scaling

suppress silent streams from interface and agent