Add git-imap-send, derived from isync 1.0.1.

Add git-imap-send, derived from isync 1.0.1.

git-imap-send drops a patch series generated by git-format-patch into an
IMAP folder. This allows patch submitters to send patches through their
own mail program.

git-imap-send uses the following values from the GIT repository
configuration:

The target IMAP folder:

[imap]
         Folder = "INBOX.Drafts"

A command to open an ssh tunnel to the imap mail server.

[imap]
         Tunnel = "ssh -q user@imap.server.com /usr/bin/imapd ./Maildir
2> /dev/null"

[imap]
         Host = imap.server.com
         User = bob
         Password = pwd
         Port = 143