Reconsidering the overwritten operators

[pc494]

Currently, almost everything that inherits from Object3d has overwritten +,-,* and / but the discussion #138 has suggested that we might want to have a careful think about how these should work.

If we are tabulating, we would expect to do int, float, tuple, list, array and other relevant orix objects, from both left and right.

I think there can't be much debate about that int and float should do the same thing, and tuple and list should be turned into numpy arrays. The main questions seem to come up about how to combine things of different dimensions. If anyone has strong generic preference we can start there, and then in a couple of days I'll see if I can write a summary of what I think would work best.