Moderators are able to send a message to the meeting's guest lobby. This new
event reaches bbb-web and is sent to the guest user with her/his status response
while polling. All guest users that are waiting for acceptance will be able to
read this message.

enableGuestLobbyMessage is disabled by default.

Adds lastAuthTokenValidatedOn to users in Akka, send it in ValidateAuthTokenRespMsg pubSub msg, makes Meteor store it as authTokenValidatedTime

Removes loginTime creation from Meteor and use the registeredOn date created on Akka. Makes Akka send the registeredOn date throught PubSub messages: UserRegisteredRespMsg, GuestsWaitingForApprovalEvtMsg and ValidateAuthTokenRespMsg.

Used by bbb-webrtc-sfu to enrich its validation on whether a user is allowed to broadcast or subscribe to a camera stream

Used by bbb-webrtc-sfu to enrich its validation on whether a user is allowed to broadcast a screen or subscribe to one

Used by bbb-webrtc-sfu to enrich its validation on whether a user is allowed to subscribe to the global audio bridge via listen only or not

Associate pads with meetings so session validation is restricted to the
meeting's valid session tokens.

Meteor will dispatch new redis events on shared notes and closed captions
pads creation. This event will go through apps and reach web to populate
a new meeting's pad collection that contains all valid pad id's for that
session. Nginx will use this collection to check if the user's session token
belongs to the pad's authorized users.

Besides these modifications, an extra change will be needed at notes.nginx.
Location /pad/p/ needs to change it's auth_request:

from /bigbluebutton/connection/checkAuthorization;
to /bigbluebutton/connection/validatePad;

Use the former Flash client avatarURL join param to replace the name
initials avatar from the user list, chat, waiting guests and connection
status list.

It is possible to define a defaultAvatarURL at bbb-web and enable/disable it

 Changes to be committed:
	new file:   akka-bbb-apps/src/main/scala/org/bigbluebutton/core/apps/externalvideo/ExternalVideoApp2x.scala
	new file:   akka-bbb-apps/src/main/scala/org/bigbluebutton/core/apps/externalvideo/StartExternalVideoPubMsgHdlr.scala
	new file:   akka-bbb-apps/src/main/scala/org/bigbluebutton/core/apps/externalvideo/StopExternalVideoPubMsgHdlr.scala
	new file:   akka-bbb-apps/src/main/scala/org/bigbluebutton/core/apps/externalvideo/UpdateExternalVideoPubMsgHdlr.scala
	modified:   akka-bbb-apps/src/main/scala/org/bigbluebutton/core/pubsub/senders/ReceivedJsonMsgHandlerActor.scala
	modified:   akka-bbb-apps/src/main/scala/org/bigbluebutton/core/running/MeetingActor.scala
	modified:   akka-bbb-apps/src/main/scala/org/bigbluebutton/core2/FromAkkaAppsMsgSenderActor.scala
	new file:   bbb-common-message/src/main/scala/org/bigbluebutton/common2/msgs/ExternalVideoMsgs.scala
	new file:   bigbluebutton-html5/imports/api/external-videos/server/eventHandlers.js
	new file:   bigbluebutton-html5/imports/api/external-videos/server/handlers/startExternalVideo.js
	new file:   bigbluebutton-html5/imports/api/external-videos/server/handlers/stopExternalVideo.js
	new file:   bigbluebutton-html5/imports/api/external-videos/server/handlers/updateExternalVideo.js
	modified:   bigbluebutton-html5/imports/api/external-videos/server/index.js
	modified:   bigbluebutton-html5/imports/api/external-videos/server/methods.js
	modified:   bigbluebutton-html5/imports/api/external-videos/server/methods/emitExternalVideoEvent.js
	modified:   bigbluebutton-html5/imports/api/external-videos/server/methods/startWatchingExternalVideo.js
	modified:   bigbluebutton-html5/imports/api/external-videos/server/methods/stopWatchingExternalVideo.js
	new file:   bigbluebutton-html5/imports/api/external-videos/server/streamer.js
	modified:   bigbluebutton-html5/imports/api/meetings/server/handlers/meetingDestruction.js
	modified:   bigbluebutton-html5/imports/api/meetings/server/modifiers/addMeeting.js
	modified:   bigbluebutton-html5/imports/api/meetings/server/modifiers/meetingHasEnded.js
	modified:   bigbluebutton-html5/imports/api/users/server/handlers/validateAuthToken.js
	modified:   bigbluebutton-html5/imports/api/users/server/store/bannedUsers.js
	modified:   bigbluebutton-html5/imports/startup/server/index.js
	modified:   bigbluebutton-html5/imports/startup/server/redis.js
	modified:   bigbluebutton-html5/imports/ui/components/external-video-player/service.js
	modified:   bigbluebutton-html5/private/config/settings.yml

This reverts commit 37ed2c75, reversing
changes made to 5af41dab.

 Currently, we user DTMF to inform the client when the call session is in echo test and when entering the voice conference.
 Unfortunately, sometimes when FS sends the DTMF, FS crashes.

 Monitor the progress of the call session using ESL events and propagate to the client.

 The client would be informed of these call states: CALL_STARTED, IN_ECHO_TEST, IN_CONFERENCE, CALL_ENDED.

 - poll FreeSWITCH for status of user so that akka-apps would be in sync with FreeSWITCH

 - add a new timestamp field on the message envelope so we can collect
   statistics on message processing times.