Label dialog event package entries for conferences.

Dialog event package entries (multiendpoint) for a conference call on
another device will have a uri something like this:
sip:conf=2001-4888-205-710f-e0-113-0-120-1466524732857069@[2001

This ends up looking nasty in the UI.  To prevent this, adding code to
detect this type of URI and set the caller name to "Conference Call",
and blank out the caller number.

See bug for screenshot.

Bug: 29534470
Change-Id: I892897ca80347f57497928cb1b02fba83c3c664a