Merge branch 'ag/send-email-imap-sent'
"git send-email" learned to drive "git imap-send" to store already
sent e-mails in an IMAP folder.
* ag/send-email-imap-sent:
send-email: enable copying emails to an IMAP folder without actually sending them
send-email: add ability to send a copy of sent emails to an IMAP folder