Major change where navigationnode contains widget configuration.

- break backward compatibility through new naming /order of the model component (db, default, plugin, widget)
- Define one Node class and remove previous definition
- Add a configurator for single panel displaying url
- Modify the cfgSvc to give access to form and grid configuration remove the method get_configuration.
- Modify the appviewport to instanciate the widget from the configuration encapsulated in the leaf.