Enhance petrinet editor capabilities

This is a story task make PetriNet editor more user friendly. We should

[x] Allow more intuitive ways to create nodes and edges
[x] Simplify edge routing, maybe just go with either linear or manhattan edges
[x] Better/more stable treatments of multi-edge situations (there are 1+ edges going from A => B)
[ ] General tweaks and UI improvements

DARPA-ASKEM / .github-private