retain backups only for 3 days; beyond that the user is responsible for copying files off of the machine
fix display of backups that are past due to be reaped
report free disk space in the admin
disable SSLv3 in dovecot now that it is known to be insecure (POODLE)

SSLv3 is already disabled in Postfix (45e93f7dcc18d588fd7725431cbc900befe33f42) and Nginx (51dd2ed70b6309ae6675653f03c2ad865fceb86d).
various improvements in bash comments
fixes for bootstrap.sh for upgrading

* `git fetch` wasn't done right for shallow clones
* the test for whether mailinabox has already been cloned wasn't looking at the right directory if the script was not run from $HOME
fix control panel when no backup has been made yet
bump bootstrap to incoming v0.04 tag
update version number in CHANGELOG
add the sa-learn permissions changes to the CHANGELOG
bring the max outgoing mail size via webmail and z-push in line with the limit set in postfix: 128 MB

The limit was previously the nginx default (2MB?).

fixes #236
Switch from SMTP+STARTTLS on port 587 to SMTPS on port 465

A good argument for using 465 is made at
https://www.agwa.name/blog/post/starttls_considered_harmful.

FastMail make a good case at
https://www.fastmail.fm/help/technical/ssltlsstarttls.html.
(https://www.fastmail.fm/help/technical/servernamesandports.html states that
587 is available but they do seem to recommend 465).

Gmail uses 465 too.

This shouldn't stop opportunistic TLS being used for incoming mail because
STARTTLS remains available on port 25 - which is what would have been used
before too.

Backward compatibility with clients that were setup to use 587 on existing
installations is maintained because we only change the setup to enable 465
 - we don't disable any existing SMTP+STARTTLS configuration.
Add support for TLS authenticated "sibling host" relayers

The use case for this is e.g. a www server that is a separate machine to
the mailinabox, but which needs to send emails to the internet - for example it
may be running Wordpress or some other web app and need to notify arbitrary
users of comments etc.

In such cases, as the www administrator is using mailinabox, they're almost
certainly better off letting mailinabox do as much as possible as far as email
is concerned (as opposed to having the www sibling host do full delivery
itself) - among other things this simplifies reasoning about DNS records.
Do not require admin as an alias for any domains, do require root for main host
Increase SPF and DMARC strictness