Allow empty edges

[nwlandry]

This PR enables empty edges. This has long been an inconsistency, since add_edges_from allowed empty edges and, for example, dual could create empty edges. This PR does the following:

• removes the exception raised for empty edges from the add_edge methods in Hypergraph and DiHypergraph and from add_simplex in SimplicialComplex.
• adds an allow_empty keyword in the remove_node methods to handle discarding empty edges created from weakly removing nodes.
• makes all the keywords in remove_node accessible as options in the remove_nodes_from methods for consistency.

This fixes #403.

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.82%. Comparing base (0475563) to head (1f22702).
Report is 53 commits behind head on main.

Files with missing lines	Patch %	Lines
xgi/core/views.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           main     #565       +/-   ##
=========================================
+ Coverage      0   92.82%   +92.82%     
=========================================
  Files         0       59       +59     
  Lines         0     4348     +4348     
=========================================
+ Hits          0     4036     +4036     
- Misses        0      312      +312     

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[nwlandry]

@tlarock and @thomasrobiglio --- let me know if you have the bandwidth to review this. The URL workflow fails, but this is corrected in an already-merged PR.

[thomasrobiglio]

Hi @nwlandry, thank you for this. I am offline for these two weeks, I will review once I'm back.

[nwlandry]

Enjoy your vacation! That sounds good.

[tlarock]

Need to make sure docstrings match function signatures re: default behaviors. Once that is done, good to go.

[nwlandry]

@thomasrobiglio --- are you still able to review this? No worries if not!