Added NameGraph extension for modular NameGraphs with an ID and edges to other NameGraphs;
Please note that adding edges to a NameGraph has been simplified: You can now create a new NameGraph with added Edges using the + operator.
This has also caused syntax changes: Two NameGraphs are now merged using the ++ operator instead of +! Lambda language was updated to reflect this modification.
Also some minor import changes are needed as the type definitions for Nodes, Edges, ... have been moved to a package object.