The current version of the SiMo extensions are available on the feature-process-discoverer-BIMP-annotation branch.

We need to be much more lenient with what the canoniser is willing to accept as input now that students are throwing weird models at it.
This commit allows unnamed flow elements, orphaned events, and unconnected data output associations.

Unconnected CPF object references are allowed.
BPMN complex gateways are allowed, even though they don't have an unambiguous CPF representation and therefore probably won't round-trip.

Don't NPE for orphaned BPMNDI elements.