Dyadic code for vector module

Has been based off #7566 
Adds code for dyadics, with tests.
Also restructures the Dyadic and Vector code into a nice Object-Oriented structure with the introduction of a common super class.
Need another indent on this line. As it is, it appears like the `not ...` is the body of the if block. See [PEP 8](http://legacy.python.org/dev/peps/pep-0008/#indentation)