Feature request: Tour map grid (rotatable)

[iantresman]

When connecting an indoor tour, I'm finding it difficult to position nodes relative to one another, because I have few "landmarks" indoors. I often know that sequences of nodes are parallel to the external walls of the building, but they are can still be difficult to align. It would be useful to be able to:

1. Enable a tour map grid
2. Set the spacing
3. Allow the grid to be moved
4. Rotate the grid (few buildings are aligned North-South)
5. Enable snap to grid

[iantresman]

Any consideration?