Refine meeting invitation emails; include VTIMEZONE

* VTIMEZONE blocks must be sent in our ics files for meeting
  invitations that are recurring, as the originator's time zone
  is critical in making attendee's calendars accurate
* Created a utility to convert TimeZone to VTIMEZONE data; the
  utility successfully generates data (including recurrence rules)
  for the entire tzinfo database (the source of TimeZone).
* Updated our ics files to include VTIMEZONE when appropriate and
  send DTSTART/DTEND in local time in that case
* Wrote some unit tests, but more are needed

Change-Id: Iccbdd00cd3b2be2da058b344ebacd17ed6fb0e3d
4 files changed