Add possibility to create graphs with duplicate nodes#53

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ccossou wants to merge 3 commits intojamesscottbrown:masterfrom

ccossou:duplicates

Commits on Feb 13, 2023

Add possibility to create graphs with duplicate nodes (i.e different nodes that have the same name).
ccossou
committed

Commits on Feb 17, 2023

Deactivate 3D effects by default for UML diagram because we can't see them properly in Yed.
ccossou
committed

Commits on Jul 5, 2023

Correct bug in groups related to allowing duplicate nodes.
ccossou
committed