docker-dev environment with a cyrus-murder setup

cyrus imap murder setup

Mount the cyrus-imap directory

Separate mupdate master

Don't set unnecessary hostnames

Inject the ip of the frontend as well

Some tweaking to make sure the frontend doesn't become a backend.

Autocreate does not work at all, I need to first create the backend
mailbox.

Set the default displayname

Support building backend from source as well

Enable csync

config.docker-dev