Closes #27

* Try to break up the C++ interface into smaller chunks

In order to make compilation less RAM intensive

* Inline the makers, also add the other sources

* Tidying up the splitting

Closes #24

Closes #23

Builds fine once version will be released

Updated the pybind11 interface

Finally done

So inconsistent in naming...

Not sure it helps...

Closing in with the models

Attach model specific methods at model construction

Dropped three more esoteric ones with good replacements

Maybe add another smarter runtime method called model that will go through the model types and return the one that is there