SIP: support colons and chevrons in display names

- fixes crash/lack of connectivity when making calls with a display
  name including colons/chevrons by quoting the display name when
  constructing the SIP contact header for both SIP and Ring
  accounts

Change-Id: I9ba03100fc95316202ab63dea2d28c93f992e432
Reviewed-by: Philippe Gorley <philippe.gorley@savoirfairelinux.com>