Document solver constants and indices, making values available in Python scripts

[ketch]

The comments in each normal Riemann solver now include:

• The number of waves
• The number of conserved quantities
• The number of auxiliary variables
• The names and indices of the conserved quantities and variables

A short script extracts these values and writes them to Python modules
so they can be imported and used in Python scripts.

Ideally, this would be implemented without the extra Python modules
by putting the Riemann solvers in modules and using module data.
This is a simple solution that doesn't require any drastic changes.

[ketch]

One example of how this can be used is here: clawpack/pyclaw#454.

[ketch]

One thing that we should discuss before/if this gets merged is what names to use for the conserved quantity (and auxiliary variable) indices. I have mainly used long names rather than mathematical symbols (e.g., "density" instead of "rho").

[mandli]

I think keeping the full names rather than the commonly used mathematical symbol names is a good idea for readability and new users. There's nothing more frustrating than taking a look at a new area and finding mathematical symbols everywhere that mean something to the experts but not to a newbie.

[mandli]

You have segfaulted nosetests, I think there should be an award for such things.

[ketch]

The strange thing is that it segfaulted after nosetests completed with all tests passing. I can't see why it could be failing since

1. The changes to fortran files are only to comments,
2. The Python files are merely constants.

I'm getting inconsistent results (different errors) when I rerun on Travis.

Any ideas?

[ketch]

Now it is passing (after I made the tests run from pyclaw/examples). I'd like to merge this (and use it in most of the PyClaw examples) if there are no objections.

[mandli]

Sounds good to me. I can merge.