api: remove getDisplayNames

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

bin/dbus/dbuscallmanager.cpp

bin/dbus/dbuscallmanager.h

bin/jni/callmanager.i

bin/nodejs/callmanager.i

src/client/callmanager.cpp

src/conference.cpp

src/conference.h

src/jami/callmanager_interface.h

src/manager.cpp

src/manager.h