Add SMS Middleware layer.

Change-Id: If5621d0c5126d6917ab00143af645692f3c4a384
SMSDispatcher: Fix determining the defaultSmsApp for proxied messages

We can't rely on the calling UID, since for re-broadcasted texts that'll
always be the telephony itself; so if called by the framework, use
the sentIntent creator to determine which app originated the message

Change-Id: I60ac02f6ae09f4260f5494659a174352f353aa2a
telephony: add SyntheticSmsMessage class

This class is used for the SMS Middleware layer taken from CM,
for Voice+ integration.
Voice+, Whisperpush: Need to send SMS_RECEIVED_ACTION for all apps.

Change-Id: I05fe3fb6dc6acea612e25d7a93d0891ad6d1754e
Fix Whisperpush and Voice+ when using the new Hangouts.

Change-Id: I1ae96354e8d5679d1e7b781875081cec08108691