lazy iterable vertex/ edge list

[mfe-]

Keeping the whole vertex /edge list in memory allocates too much space in some scenarios. When iterating over vertices /edge list, it should be possible to outsource them (for example into a file by using the existing deserializing function or simply save the guid of the vertex or edge).

• [ ] Implement outsourcing part of the vertice/edge list by saving them into a file.