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.

 - We had an issue where FreeSWITCH, for some unknow reason, stopped recording the voice conference
   in the middle of the meeting while there are users in the voice conference. We've relied on the
   voice conf started event to trigger recording of wav files. This event is sent when the first user
   joins the voice conference. In this case, there was no voice user joined after the recording stopped
   as there were already users in the voice conference. TO make sure that the audio is recorded, akka-apps
   will send a "check if voice conf is running and recording" message to FreeSWITCH every 30sec. If akka-apps
   receives a "running=true recording=false" response from FreeSWITCH, akka-apps will send a start recording
   msg to FreeSWITCH.

   most of the CPU that users takes a long time to load the client and join. This
   way, we can detect if there are a number of users failing to join the meeting.