Run coverage tools and remove *all* unused code

There's a lot of unused code in drp_stella and it needs to be removed. Let us start by running a python coverage tool on all the "live" command line tasks, and remove all code that doesn't get used (subject to some sort of sanity test). This should cover unused swig wrappers as well as unused python code.

Then, after that, run a C++ coverage tool (e.g. tcov) and remove all C++ that isn't used.