[VM] Differences between IMAP-FCC and FCC

[blueman]

1. Is there any reason that IMAP-FCC doesn't include a 'From:' line whereas
   FCC does include a 'From:' line? The net result is that for IMAP-FCC,
   the vm summary gets the sender from the "from" line which is often then
   the meaningless "VM"

2. IMAP-FCC allows multiple comma-separated fcc imap folders, while FCC
   only seems to allow a single file entry. Would it make sense to
   transfer over the same parsing functionality to FCC as exists in
   vm-imap-save-composition