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) add VIEW action and BROWSABLE category to SmsSendtoActivity intent filter
2) created class Rfc5724Uri for processing RFC5724 SMS URIs
3) added a set of tests for new Rfc5724Uri class
4) updated SmsSendtoActivity to use Rfc5742Uri for processing VIEW intents
Fixes#2578Closes#3030
// FREEBIE
