roundcube Bug Fixes:
Fix for Cross-Site Scripting (XSS) via HTML messages with malicious CSS content
General Improvements from roundcube's Issue Tracker
* drop the ondrej/php PPA since PHP 7.x is available directly from Ubuntu 18.04
* intall PHP 7.2 which is just the "php" package in Ubuntu 18.04
* some package names changed, some unnecessary packages are no longer provided
* update paths
@joshdata squashed pull request #1398, removed some comments, and added these notes:
* The old init.d script for the management daemon is replaced with a systemd service.
* A systemd service configuration is added to configure permissions for munin on startup.
* nginx SSL settings are updated because nginx's options and defaults have changed, and we now enable http2.
* Automatic SSHFP record generation is updated to know that 22 is the default SSH daemon port, since it is no longer explicit in sshd_config.
* The dovecot-lucene package is dropped because the Mail-in-a-Box PPA where we built the package has not been updated for Ubuntu 18.04.
* The stock postgrey package is installed instead of the one from our PPA (which we no longer support), which loses the automatic whitelisting of DNSWL.org-whitelisted senders.
* Drop memcached and the status check for memcached, which we used to use with ownCloud long ago but are no longer installing.
* Other minor changes.
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
* Install PHP7 via a PPA, enable unattended upgrades for the PPA, and switch all of our PHP configuration to the PHP7 install.
* Keep installing PHP5 for ownCloud/Nextcloud packages because we need it to possibly run transitional updates to ownCloud/Nextcloud versions less than 12. But replace PHP5 packages with PHP7 packages elsewhere.
* Update to Nextcloud 12 which requires PHP7, with a transitional upgrade to Nextcloud 11.0.3.
* Disable TLS cert validation by Roundcube when connecting to localhost IMAP and SMTP. Validation became the default in PHP7 but we don't necessarily have a (non-self-)signed certificate and it definitely isn't valid for the IP address 127.0.0.1.
Merges #1140
