Fix nested iteration of `openvpn_clients`.

fixes issue #734

an improved version of PR #696

The `owncloud` metapackage also installs dependencies such as Apache.
To avoid version problems, just install ownCloud.

- remove configuration of OpenDKIM
- remove OpenDKIM milter from postfix's configuration
- add configuration files for rpsamd's dkim module
- update the rspamd task
- update services in README

- Remove OpenDMARC
- Configure Rspamd for DMARC handling
- Update services and how to set up DNS records in README

resolved issue #721

Sometimes logwatch logs will contain URLs and domain names that trip
on abuse lists.    Use a custom filter to remove these checks.

Password is not necessary when using a trusted
connection (localhost).  Tested by moving mail in and out of Junk
folder while monitoring `/var/log/rspamd/rspamd.log`.

Rmilter [is no longer
needed](https://rspamd.com/doc/quickstart.html#rmilter-setup) as of
Rspamd 1.6.

The configuration file `90-plugin.conf` exists but was not getting
installed.

rmilter fails to start due to a missing trailing semicolon.

there is a missing semicolon that causes rmilter not to start with error:
"config file parse error! line: 156, text: tempdir, reason: syntax error"

which, as expected is the following line

Update for Debian 9

The stock rspamd package provided by Raspbian (jessie) is at version 0.6.10.  The rspamd repository doesn't offer binaries for the armhf architecture (e.g., Raspberry Pi 3) in order to get a more recent package.  Instead, use the yunohost repository for rspamd package (currently at 1.3.5) on armhf.

Implementing password hashing inside password_hash filter plugin

Restart prosody after LE cert renewal

Add group name ssl-cert for SSL certificates

Use postmaster@ for DMARC reports

Switching to Ansible 2

* Install Python 3 pip and cgit dependencies
* Update to cgit 1.1
* Correct Ansible tag syntax for recent versions of Ansible

Avoid opportunity for copy-paste trouble