Handling "webcamsOnlyForModerator" meeting option in the client.

...button-client/src/org/bigbluebutton/core/model/Meeting.as

...client/src/org/bigbluebutton/core/model/MeetingBuilder.as

...ent/src/org/bigbluebutton/main/model/users/JoinService.as

...g/bigbluebutton/modules/users/services/MessageReceiver.as