Make REMOTEID optional in FETCH responses.
Review Request #111593 - Created July 19, 2013 and submitted
Rather large diff since I needed to restructure FetchHelper a bit to make the changed parts easier to unit-test. RID just like any other optional property is still queried from the DB, that's a follow-up fix.
Unit-test & using KMail. The asapcat test case shows a 5% decrease in transfer volume.