Office to PDF conversion failed message

Unify user-list content style

Pulled HTML5 locales Feb 14, 2020; Added Thai

Add health check for akka fsesl

 - clean up
 - bind to port 8900

 - bind only to localhost

Merge branch 'v2.2.x-release' of github.com:bigbluebutton/bigbluebutton into add-health-check-for-akka-fsesl

 Track call session state

 The /healthz returns information is we are able to send and receive message to/from freeswitch.
 The /status returns information about freeswitch version and uptime.

Several fixes for the external video module

Increase the pingpong removal timeout to reduce false positives

 Breakout rooms shouldn't call the end meeting callback url

 - add check if the meeting that ended isn't a breakout room and if there is an end-meeting-callback-url.

Webhooks fixes

 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.