Protocol for algorithms on both real and complex numbers

[NevinBR]

We should have a protocol that floating-point types as well as Complex conform to, which includes multiplication and division. This will enable people to write more useful generic algorithms for those types.

One option is a protocol (perhaps named Field) that refines Numeric and includes division. Then algorithms could be written against either Field or Field & ElementaryFunctions.

[stephentyrone]

Note that a Field protocol necessarily falls out naturally when we add a linear algebra module, so this is something that will have to happen in the short-medium future. I'm just kicking the can down the road until Real and Complex stabilize a little bit.

[NevinBR]

Will we want the Real protocol to refine Field?

[stephentyrone]

Most likely.

[stephentyrone]

#91

[stephentyrone]

Merged to master (with the imperfect name "AlgebraicField").