Documentation and guidance for Nash equilibrium algorithms

[tturocy]

For historical reasons, the documentation on the equilibrium-finding algorithms has been scattered. It was originally concentrated in the "manpage" style documentation on the command-line tools - although coverage of the actual algorithm practicalities was very mixed.

As the command-line tools are less important, and accessing these is done either principally via the GUI or pygambit, we have created a separate section for the algorithms themselves.

We are still however maintaining the "manpage" docs for the command-line tools, even though these are now actually just wrappers around the Python calls. Nevertheless, the behaviour of the command-line switches there does need documenting separately.

sphinx-click would take care of automating the currently-manual documentation of the actual switch behaviour. But, part of this exercise also needs to check that we still don't have any algorithm description text that's in the algorithm "manpages" that shouldn't be shifted to flesh out the operational description of the methods.