conference: add account preference to enable moderation for all

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

bin/dbus/dbusconfigurationmanager.cpp

bin/dbus/dbusconfigurationmanager.h

bin/jni/configurationmanager.i

configure.ac

src/account.cpp

src/account.h

src/account_schema.h

src/client/configurationmanager.cpp

src/conference.cpp

src/dring/account_const.h

src/dring/configurationmanager_interface.h

src/manager.cpp

src/manager.h