Email flag refinement redux
This ensures that when normalising a folder unread status changes are not counted twice and that when moving email (actually implemented as a copy+delete), that the message has its deleted flag cleared in the new location. As a bonus also fixes the unread count flickering on folder open.
Fixes #213 (closed), https://bugzilla.gnome.org/show_bug.cgi?id=713910 and also https://bugzilla.gnome.org/show_bug.cgi?id=713165