Configuration file needs to belong to prosody user

also fix  fix php-sqlite3 package name

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

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.

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