Direct access to DependencyGraphBuilder
Adapt to different DependencyNode types
New GraphFactory to create real graphs instead of trees.
It's complicated:
- DependencyGraphBuilder does actually only create dependency trees
  because it shows only the effectivly used dependencies
- DependencyTreeBuilder is capable of creating dependency graphs because
  it shows all dependencies
Class rename (part 1)
Class rename (part 2)
Add "tree" mojo