conference: add mute participant for moderator

bin/dbus/cx.ring.Ring.CallManager.xml

bin/dbus/dbuscallmanager.cpp

bin/dbus/dbuscallmanager.h

bin/jni/callmanager.i

bin/nodejs/callmanager.i

configure.ac

src/call.h

src/client/callmanager.cpp

src/conference.cpp

src/conference.h

src/dring/callmanager_interface.h

src/manager.cpp

src/manager.h

src/media/audio/ringbufferpool.cpp

src/media/audio/ringbufferpool.h

src/string_utils.cpp

src/string_utils.h