Mms: Add privacy mode notifications

This add privacy mode feature to notifications, user and message are hidden in
status bar and notifications area when privacy mode is enabled

Patch set 1-4 : Initial commits
Patch ser 5   : Slight wording change of summary string

Patchset: default value to off

Change-Id: I20f5fd198d51d7079345708725a58ef2c2a71b7f