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