Sync X-Keywords to labels in one direction (offlineimap -> sup)
Attempt to add write-back X-Keywords support
Refactor change
Semi-working write-back keywords support
Working support for syncback of labels to gmail via offlineimap, plus hack for enabling "sendmail -f" to set the envelope sender.
Clean up PR
Revert sendmail hack, handle some other maildir flags better
Quick hack to pass -f to sendmail to set the envelope sender.
Merge branch 'sendmail_hack' into develop