Mms: Fix can't refresh receipent name

Contact cache isn't updated after contacts database changed and
the receipent name can not be get from Contact.getName().

Following the change or CR652842,
Add ContentObserver for change of contacts database.
Update sim messages after the cache updated.

CRs-Fixed: 745992

Change-Id: Ief93a95ca0b94123474e590c2ce1626554a97f15