Differences from my obsolete Prim Grid library include:
- DG offers a direct grid2d_Grid derivative with a cleaner interface.
- Edge wrapping can be toggled at will instead of on creation/reset.
- Connections can be made manually with coordinates and/or directions rather than bits or hidden indices.
- Prim's algorithm is still provided, but whether or not the connections reciprocate can be determined within each proc call.
- Various cell categories can be identified and gathered.