Basic Vector framework

Added:

1. Vector core - Vector, VectorAdd, VectorMul, BaseVector
2. BaseScalar
3. Del
4. CoordSysRect
5. Point
6. functions.py - express, matrix_to_vector 
Why is it that we need this? What are the use cases for having Del attached to each coordinate system?

Also, why are we having so many circular dependency issues? I would think with a fresh module design, this wouldn't be the case.