More efficient sync

[Fizzadar]

Currently we fetch the whole UID list for all emails in a given folder every sync. For the archive folders this may consist of hundreds of thousands of UIDs, take a while to return and be fairly large in side.

Fetching the whole UID list is important to capture when UIDs/emails have been deleted, but this needn't happen all the time. Additionally we can filter by date to reduce the scope of fetched UIDs, and perhaps with a less often "full sync".