Merge branch 'riadvice-change-user-role-bbb-web' into v2.0.x-release

...bluebutton/core/apps/users/ChangeUserRoleCmdMsgHdlr.scala

...scala/org/bigbluebutton/core/models/RegisteredUsers.scala

...b/src/main/java/org/bigbluebutton/api/MeetingService.java

...org/bigbluebutton/api2/bus/ReceivedJsonMsgHdlrActor.scala

...g/bigbluebutton/api2/meeting/OldMeetingMsgHdlrActor.scala

...bigbluebutton/modules/chat/views/ChatMessageRenderer.mxml

.../bigbluebutton/modules/users/views/MediaItemRenderer.mxml