Port 8080 only has to be accessible internally as it is forwarded by the
nginx proxy.

Add files from opsone infrastructure to .gitignore and dummy for adapting
nginx configuration

In order to ease upgrades the optional declaration of the JRE/JDK
installation to use is removed:

https://gerrit-review.googlesource.com/Documentation/config-gerrit.html#container.javaHome

Switch to named volumes for cache, db, git, index and logs in order to
improve future compatibility with cloud services like Kubernetes. Move
etc and ssh from volumes to assets as they shall be versioned but
Gerrit may change contents. This means in future extra care has to be
taken when executing docker-build as changed contents inside the
container will be discarded.

In order to keep a clean git state on the server the secure.config
is moved to secure.config.example. In a second step secure.config will
be added to .gitignore. Then secure.config may contain the real
configuration and secure.config.example serves as what it was thought
to be: an example to which secure definitions have to be done.

Add a theme for PolyGerrit UI specifying a TYPO3 logo in the header,
"privacy policy" and "legal notice" links in the footer.

Remove theme definitions and files used for old GWT UI and the old
workaround to set the "Report Bug" URL for "legal notice".