New way to generate interface code for CreateInterfaceWizzard based on
AST tree and nodes.

This is draft only and should be completed later, to correct work
required changes in PDT (https://git.eclipse.org/r/#/c/21649/). I added
some basic test based on PDTT files. 

Todo:
- handling "use" statements.
- handling "add comment" flag
- fixed wrong namespaces for global interfaces in "extends" part