Make fit template previews more visible in the docs

[wtbarnes]

There are a bunch of jpegs that show previews of what lines the various fitting templates target for different solar conditions (QS, AR, etc.). These are currently buried in the package and not easily visible in the documentation.

They should be moved elsewhere (maybe docs/_static?) and be rendered on a separate page in the docs with an appropriate TOC so that it is easy to preview the different templates.