1) Move contact URI, contact photo URI, and custom label
into recipient database, so there are no longer any
contact DB queries during Recipient object loading.
2) Use a SoftHashMap so that any referenced Recipient objects
can't get kicked out of the cache.
3) Don't load Recipient objects through the provider during sync.
This was a super expensive thing to do, and blew up the cache.
4) Only apply changes to Recipient objects during sync if they
are in the cache. Otherwise, there should be no outstanding
references, and the changes are fine going exclusively to
the DB.
