This commit is doing some of the basic stuff Oscar talked about.

1. Renaming C/Ab -> Commutative
2. Adding convenience methods to companion objects
3. Removing Trig

I am deferring on removing Additive/Multiplicative/EuclideanRing,
since it's possible that after some change we may want to keep those.

This is a work-in-progress.
Get most of the rest of the packages converted.

Still to do:

 1. Consider removing some additional files
 2. Break things out into sub-packages and sub-projects
 3. Write some tests
add functions to IsReal