Handle layout of temporal containers nested in abstractive containers

[ryanholmdahl]

In this case, we have edges that connect the contents of temporal containers to their containers, to an abstractive container. This breaks layout functionality for several reasons:

1. layout.layoutTemporalContainers() will cause the edge to shift downwards when the temporal container is expanded, no longer connecting to the rim of the container.
2. layout.layoutGraphRecurse() will break, as the abstractive container will be laid out, but it will contain edges connecting itself to its children, which causes ELK to raise an exception.

Required fixes:

• In layout.layoutTemporalContainers(), when edges are being shifted, check if the edge connects to the temporal container output or input port, and freeze its appropriate endpoint.
• Our stopgap fix (already implemented) is to clear the edge list of an abstractive container if it contains temporal containers. This causes no error to be raised, but leads to some ugly-looking lines and is likely not robust. I'm not sure what the best solution is here.