1) Switch back from AsyncTasks to an Executor and Futures.
2) Make the Executor operate LIFO.
3) Make the Executor thread a BACKGROUND_PRIORITY thread.
1) Refactor recipient class to support asynchronous loading operations.
2) Refactor recipient factory to simplify recipient access.
3) Consoliate everything into one recipient provider that is capable of
doing async lookups and intelligent caching.
1) Change the MessageSender logic so that individual SMS messages
are encrypted whenever there is a secure session, unless the UI
explicitly specifies otherwise.
2) Change the MMS logic so that messages to a recipient with a
secure session are all sent individually, instead of including
those recipients into the batch plaintext message.
This requires a few changes to Recipient in order to make sure we
have a Contact URI at click time. While we're at it, let's git rid
of the OldRecipientProvider, which was for pre-2.0 contact stuff
(no longer supported, woohoo!).
The 1.X Android versions don't have the 2.X VERSION_CODE
symbols, so comparing against them in order to make 1.6
choices will throw runtime exceptions.
