[Feature Request] Call undirected edges in FGL.ArrayAdjacencyGraph

[LibraChris]

At the moment in order to call an edge you need to call the edge with a designated source and target (As explained in #50 ).
Adding functionality to call edges independent from this source/target designation will allow for easy calling of undirected edges.

[LibraChris]

• Add simple functions to call undirected edges(Added simple functions to get undirected Edges. #58 )

• Add functions to edit undirected edges

• Add functional calls for undirected edges