In 0088fb45 I changed the management daemon's startup
script from a symlink to a Python script to a bash script that activated the new virtualenv
and then launched Python. As a result, the init.d script that starts the daemon would
write the pid of bash to the pidfile, and when trying to kill it, it would kill bash but
not the Python process.

Using exec to start Python fixes this problem by making the Python process have the pid
that the init.d script knows about.

fixes #1339

Same as in a52c56e5.

Fixes #1338.

free_tls_certificates uses acme.jose, which in acme v0.21 was moved to a new Python package.

See #1328

We don't have the virtualenv this early in setup.

Broken by 0088fb45.

Fixes #1326.

See https://discourse.mailinabox.email/t/that-is-not-a-valid-email-error-during-mailinabox-installation/2793.

no need to do a second apt-get update after 'installing' the PHP7 PPA if the PPA was already installed

The cryptography package has created all sorts of installation trouble over the last few years, probably because of mismatches between OS-installed packages and pip-installed packages. Using a virtualenv for all Python packages used by the management daemon should make sure everything is consistent.

See #1298, see #1264.

The PHP5 packages have a dependency on (apache2 or php5-cgi or php5-fpm), and since removing php5-fpm apache2 started getting installed during setup, which caused a conflict with nginx of course.

These packages don't seem to be needed by Roundcube or Nextcloud --- Roundcube includes the ones it needs.

see #1264, #1298

fixes #1300

A quick fix - there's no "o" option for free.

To enable users to do custom spam filtering based on score, it's helpful to render the actual spam score as a float in a separate header rather than as part of X-Spam-Status where it only appears in a comma separated list.

See https://roundcube.net/news/2017/11/08/security-updates-1.3.3-1.2.7-and-1.1.10.

merges #1287

Old kernels can build up and some packages may not be needed anymore.

See https://discourse.mailinabox.email/t/storage-space-decreasing/2525/5.

the information about the invalid link comes from here -> https://discourse.mailinabox.email/t/admin-sync-guide-contacts-and-calendar-davdroid-3-69-free-here/2528

update nginx cipher list to Mozilla's current intermediate ciphers and update HSTS header to be six months

* The Mozilla recommendations must have been updated in the last few years.
* The HSTS header must have >=6 months to get an A+ at ssllabs.com/ssltest.

fix dns regex: underscores are allowed in domain names even though they are not allowed in hostnames

Nextcloud 12 adds a new OC_VersionCanBeUpgradedFrom field to /usr/local/lib/owncloud/version.php which lists
prior NC/OC version numbers, which confuses our check for what the installed version is. Make our regex more strict.

merges #1238

merges #1216