Fix definition.xml pretty printing on OSX Mavericks.

On Mavericks most of the definition.xml was writte onto a single line.

Removing the tail of staticly inserted nodes fixes this issue because it seems to change
the behavior of pretty printing in newer libxml2 versions.
Merge pull request #48 from 4teamwork/jone-pretty-print

Fix definition.xml pretty printing on OSX Mavericks.
Extract role translation functions into utils.

- ftw.lawgiver.utils.generate_role_translation_id
- ftw.lawgiver.utils.translate_role_for_workflow