Case Modeller does not add connectors between nodes.

When opening a BPMN2 file that uses features not available in CM the nodes and connectors are not rendered on the Canvas; although remain in the Graph. When a "visible" (i.e. supported) node is deleted we need to ascertain the chain of "invisible" (unsupported) nodes and edges to delete from the Graph.

When a new BPMN2 file is created it has a "Start Node" by default. When a new Stage is added it is not currently connected to the "Start Node" (nor subsequent Stages connected to other Stages). Activities are not connected at all.

We need to review when, how and where etc connectors are created and destroyed!