revert dovecot part of 39bca053 because dovecot started behaving weird and I don't have time to debug it

nginx/postfix use a new pre-generated dh2048.pem file. dovecot generates the bits on its own.

ssllabs.com reports that TLS_DHE ciphers went from 1024 to 2048 bits as expected. The ECDHE ciphers remain at 256 bits --- no idea what that really means. (This tests nginx only. I haven't tested postfix/dovecot.)

see https://discourse.mailinabox.email/t/fips-ready-for-ssl-dhec-key-exchange/76/3

see https://github.com/mail-in-a-box/mailinabox/commit/8e0967dd8e2ecce6a1092deaca7241a6d927ae1e#commitcomment-7940724

add strict SPF and DMARC records to any subdomains (including custom records) that do not have SPF/DMARC set

closes #208

fixes #206 (hopefully)

fixes #195

don't allow catch-all addresses in the admin because they take precedence over mail users and that's counter-intuitive

For now use the command-line tools/mail.py if you need it.

see #200

Revert "Changed incomming-email-input to type text"

This reverts commit 9631fab7.

see http://discourse.mailinabox.email/t/activesync-z-push-not-working/94/3

see https://discourse.mailinabox.email/t/set-www-a-and-other-dns-records-after-install/63/10

don't run `apt-get update` when generating the status checks output because it is so slow and should be update daily by cron anyway

https://discourse.mailinabox.email/t/opening-up-a-custom-port-for-ssh-after-install/55/2

revise the description of A records on domains: the A record must be present for good deliverability so that the envelope domain resolves, but it doesn't have to resolve to this machine

add link to contributors, remove duplicate "to"s

Changed incomming-email-input to type text

The input type="email" validation won't allow "@example.com", which is needed for catch-all-aliases.

update roundcube version

In the event the first user is an address that we'd normally create as an alias,
we'd generate a loop from the alias to the administrative alias to the first user
account (which was the alias again).

hopefully fixes #186

only hold onto backups for 14 days (not 31) and show when the backups will be deleted in the control panel