rename the scripts directory to setup

Conflicts:
	setup/dkim.sh
	setup/dns.sh
	setup/dns_update.sh
	setup/spamassassin.sh
	setup/start.sh
move management into a daemon service running as root

* Created a new Python/flask-based management daemon.
* Moved the mail user management core code from tools/mail.py to the new daemon.
* tools/mail.py is a wrapper around the daemon and can be run as a non-root user.
* Adding a new initscript for the management daemon.
* Moving dns_update.sh to the management daemon, called via curl'ing the daemon's API.

This also now runs the DNS update after mail users and aliases are added/removed,
which sets up new domains' DNS as needed.

Conflicts:
	setup/start.sh
on second and later runs of start.sh, recall the inputs the user entered the last time

Conflicts:
	setup/start.sh
remove vestigal docker compatibility that prevented starting services during setup
Mask password input on stdin

Conflicts:
	tools/mail.py
Protect private key from being world-readable

Postfix, Dovecot, and nginx all read the key file while they're running
as root — before dropping permissions — so no authorization is needed on
the private key file beyond being root-readable.

Conflicts:
	setup/mail.sh
use editconf.py to mangle /etc/postfix/master.cf

* using it to enable the Postfix submission service
* per @mkropat's suggestion in #69, set an option to distinguish submission from regular smpd in syslog by giving submission a new name (doing this here to test that editconf is working right on master.cf)

Conflicts:
	setup/mail.sh
Filter privacy-sensitive headers on outgoing mail

This re-implements part of PR #69 by @mkropat, who wrote:

By default, Postfix adds a Received header — on all mail that you send —
that lists the IP of the device you sent the mail from.  This feature is
great if you're a mail provider and you need to debug why one user is
having sending issues.  This feature is not so great if you run your own
mail server and you don't want every recipient of every email you send
to know the device and IP you sent the email from.

To limit this filtering to outgoing mail only, we apply the filters just
to the submission port.  See these guides [1] [2] for more context.

  [1] http://askubuntu.com/a/78168/11259
  [2] http://www.void.gr/kargig/blog/2013/11/24/anonymize-headers-in-postfix/
reorganize mail.sh a little

Conflicts:
	setup/mail.sh
increase the postfix message size limit from 10MB to 128MB
Replace php5-cgi with php5-fpm
strengthen the cyphers and protocols allowed by Dovecot and Postfix submission