Fix typos in backup status template

Fix typo in mail-guide.html

Sercurity -> Security

catch-all aiases and domain aliases should not require postmaster@ and admin@ aliases because they'll forward anyway

internationalized domain names (DNS, web, CSRs, normalize to Unicode in database, prohibit non-ASCII characters in user account names)

* For non-ASCII domain names, we will keep the Unicode encoding in our users/aliases table. This is nice for the user and also simplifies things like sorting domain names (using Unicode lexicographic order is good, using ASCII lexicogrpahic order on IDNA is confusing).
* Write nsd config, nsd zone files, nginx config, and SSL CSRs with domains in IDNA-encoded ASCII.
* When checking SSL certificates, treat the CN and SANs as IDNA.
* Since Chrome has an interesting feature of converting Unicode to IDNA in <input type="email"> form fields, we'll also forcibly convert IDNA to Unicode in the domain part of email addresses before saving email addresses in the users/aliases tables so that the table is normalized to Unicode.
* Don't allow non-ASCII characters in user account email addresses. Dovecot gets confused when querying the Sqlite database (which we observed even for non-word ASCII characters too, so it may not be related to the character encoding).

see https://discourse.mailinabox.email/t/multiple-domains-in-mail-in-a-box-with-the-domains-being-hosted-elsewhere/56/18

/proc/meminfo reports kibibytes. Lower the minimum memory requirement so that 768 MB (not MiB) also is allowed.

Report the detected memory in MB (not KiB), to be clearer.

Fixes #289.

If bind9 isn't running, dont proceed with other checks because we can't do DNS checks. Even though we skip, add error handling so that a failed call to rndc doesn't crash and that a timeout in a DNS check doesn't crash the status checks.

partialy reverts 93a722f8; closes #287

explain how to add SRV records to DNS zonefile using the API

see https://discourse.mailinabox.email/t/create-srv-record-at-the-dns-server/225

see https://discourse.mailinabox.email/t/postgrey-and-ipv6/227

See https://discourse.mailinabox.email/t/mailserver-limits/228.

see https://discourse.mailinabox.email/t/local-dns-is-not-working-was-unable-to-check-system-status/165/39

admin: ensure multiple concurrent api calls dont confuse the ajax loading indicator (track number of open requets, stop fade animation when it is time to hide)

Fix NS status check - should sort on both ends of the comparison

explain how to install a multi-domain or wildcard ssl cert; if one is installed, the Replace Cert button in the admin for non-primary domains should not replace the cert on the primary domain

add `apt-get install sudo`

not all setups have it and the miab installer depends on it

Relative hostnames have a fall-back lookup with the machine's hostname appended, which makes no sense. Add a period, e.g. "my.hostname.com" => "my.hostname.com.", to prevent that.

This caused false positive Spamhaus checks. Fixes #185.