Eliminate the concept of 'Recipients' (plural). There is now just
a 'Recipient', which contains an Address that is either an individual
or a group ID.
MMS groups now exist as part of the group database, just like push
groups.
// FREEBIE
This was a holdover from Signal's origins as a pure SMS app.
It causes problems, depends on undefined device specific behavior,
and should no longer be necessary now that we have all the
information we need to E164 all numbers.
// FREEBIE
1) The system does actually enforce having a BROADCAST_SMS
permission on the SMS receiver. Break out the "delivered"
parts of this into a separate Receiver, so the permission
won't trip up GB devices.
2) The system does actually enforce having "quick response"
intents. Add a no-op for now.
3) Add a "make default" prompt.
4) Update settings to reflect what's going on in KitKat.
