Unneccessary empty lines

[weclapp-dev]

This combination

final OutputFormat format = OutputFormat.createPrettyPrint();
format.setTrimText(false);

the XMLProviders leads to additional empty lines after each xml tag.
There are three possibilities to solve:

1. Keep it like it is - the files are still valid
2. Use createCompactFormat instead of createPrettyPrint and keep the formatting in the strings to build the xml
3. Remove the formatting in building the xml tags and just let the ouputFormat do the pretty printing (favorite).

[jstaerk]

Thanks for your PR, I'll have a look, probably tomorrow. Unfortunately the original reason why I disabled parts of the auto formatting (XRechnung #238) does not yet have an automatic test.

[jstaerk]

what problems do I have it works like a charm