Implement getVertices
Store Edges in the simple BiDigraph

This should make edge retrieval much more efficient
Hashable instances
Unsafe edge label read
Conversion to ST
Switch to unsafeGetEdgeLabel
Split APIs a bit more to support inductive graphs
Draft implementation of inductive graphs
Add a bit of documentation
Instances for the label adapters
Default implementations for some interfaces
'context' method for inductive graphs

This could be implemented in terms of match, but it feels
more efficient to have it on its own.