Simplify CodeGenerator / Strategy / Navigator / Visitor

[gossi]

This is still code from the old cg-library. Yet I added CodeGenerator in front of it and gave it a nice API to work with. While the Visitor Pattern still seems very good in that situation, it still looks too complex in total. Should be simplified by any means.

Ref #23

[gossi]

Things to think about:

• Divide GeneratorVisitor into smaller chunks so it can be used for testing to generate PhpParameter or PhpProperty, etc. code
• extract sorting to config, having something like this: CodeGenerator(['sortMethods' => false]) to even deactivate sorting. Maybe provide some presets for sorting.