Create Asciidoctor extension for gettting package names

[lordofthejars]

Issue Overview

Currently in several parts of the documentation, we are hardcoding the fully qualified class name. So if we refactor the package then the documentation becomes outdated.

Expected Behaviour

Creates an asciidoctor extension for reading package and classname from file directly.
In case of the file is not found we can log a warn message.

Current Behaviour

We need to hardcode the package.

[bartoszmajsak]

In case of the file is not found we can log a warn message.

Shouldn't we fail the build to fix it?

[lordofthejars]

I know that this would be the logical thing, but if you notice all in Asciidoctor does not fail but just shows warnings. Asciidoctor always tries to do its best not failing. You can test it for example with callouts, you can define a callout that does not exists and you'll receive a warning but not an exception.

[bartoszmajsak]

Ok, that is fine. Then I guess we should adjust the build script to fail if such pattern occurs.