Basic vector code, without a coordinate system class

All calculations essentially occur in the same frame.
i, j, k and x, y, z are imported as base vectors and base scalars by default on importing sympy.vector.
delop is a Del operator instance.

Example:

>>> v = 3*i - j
>>> delop ^ v
0

(delop ^ v represents curl of v)
I see, the point is that overwriting `__hash__` and `__eq__` baffles me. I think that it's better to restructure these objects.

For what I see, the mathematical characterization of this object is provided by the tuple `(1, index, coord_system)`. This object then associates a `name`, which is in a 1-to-1 correspondence with the ID tuple.

I'm not sure that this is the best approach to this. I think that the parameters passed to the constructor should uniquely identify the object. The problem is if this object should be identified by just `name` or `id` or by both `(name, id)`.

In the diffgeom module the equivalent of this problem is handled by identifying the object by `id` only, i.e. `(index, coord_system)`, while `name` is just an optional formatting parameter used by the printer. Instead of having `super(..., cls).__new__(cls, name)`, there would be `super(..., cls).__new__(cls, index, coord_system)`, in such a way there would be no necessity of overwriting `__hash__` and `__eq__`.