Support multi-level UIWizard flows.

Say for instance I want to create a new entity, but persistence is not set up. I should have the choice to set up persistence, say, via a checkbox.

but once persistence is set up, then I should be directed to add a new field, for instance. So the flow is this:

1. New Entity
2. Persistence Setup (Container Selection, Provider Selection)
3. New Field

This means that persistence setup executes in a sub-flow that must return to the next designated step of the original flow when complete.

return Results.navigate(PersistenceSetup.class, NewField.class)