Cran cleanup 2

The biggest change is removing more exports. 

I’d like to keep the external API as simple as possible for now.  The internal functions are documented, and users are free to find and use them, but I don’t want to make the promise that these functions will be there in future releases.  I want the flexibility to re-work the internal API.

We can release the internal API piece by piece as it matures and solidifies.