Add option to use linear solver for banded matrix and document solver arguments

[astoeriko]

I added an option for another linear solver implemented in SUNDIALS that is specialized for banded matrices. When the right-hand-side function has a banded structure, using this linear solver can speed up the ODE solver considerably.

In addition, I started documenting the arguments of the Solver.

Any feedback on the changes (including the documentation and test) is very welcome. :-)

[aseyboldt]

@maresb Any idea why the tests aren't running?

[maresb]

@aseyboldt, it looks to me like it's running but failing on Windows Python 3.9. Occasionally I encounter a website view glitch in GitHub when monitoring the test runs.

As for the failure, somehow the "Build package" task is trying to select pypy3.9 >=7.3.15, but numba doesn't support pypy.

I'm fairly baffled about where Pypy is coming from. I also don't really understand the point of building sunode as a Conda package here. (Usually one just leaves that to the feedstock and installs it via pip in the CI, possibly within a Conda environment.)

[aseyboldt]

@aseyboldt, it looks to me like it's running but failing on Windows Python 3.9. Occasionally I encounter a website view glitch in GitHub when monitoring the test runs.

Looks like that might have been it, thanks...

I'm fairly baffled about where Pypy is coming from. I also don't really understand the point of building sunode as a Conda package here. (Usually one just leaves that to the feedstock and installs it via pip in the CI, possibly within a Conda environment.)

Same here. I think building the conda package is some leftover from times back, I don't even remember what the reason was. I'll make a separate PR that switches to just installing the deps using conda, but installing sunode as a normal python package.

The problem shouldn't be related to this PR though, so I think we can just merge and figure out that problem in the upcoming test PR...

@astoeriko Thank you for the PR (and especially the docs ;-) )