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)
Yeah. I had my doubts about the naming too. If I am not wrong, one of those Symbols conflicts with those for the square-root of one. But does it make sense for a user to mix-up complex numbers and vectors? I am not sure of a use-case for this. In any case, these default Symbols will be gone after CoordSysRect is coded. But till then, can you suggest better names for these?