Refresh documentation

[mperrin]

Documentation issues checklist

• Remove commented text from webbpsf.rst (and elsewhere)
• Mention :py:attr:JWInstrument.options where appropriate in webbpsf.rst Instrument options keyword argument doesn't validate option names #24
• Update instrument subclassing example (refers to webbpsf.TFI, ThinLens without radius)
• Move poppy.rst into POPPY (if there's information there that isn't already in the POPPY docs). Should leave just enough discussion in webbpsf docs to explain at a high level what POPPY is and how it is used in WebbPSF, just so that WebbPSF users can have some technical sense of how it works under the hood without having to jump to the full POPPY documentation.
• Change the module index to link directly to the webbpsf module page
• Remove all mention of Python 2.6.x support Remove all mention of Python 2.6.x support #27
• Explain (or explain in POPPY docs and link to) how to set use_multiprocessing Docs: "Performance and Parallelization" appendix out of date #23
• Set up intersphinx for references to POPPY
• Link to poppy.Instrument options attribute docs from JWInstrument (depends on intersphinx?)
• Add documentation for image jitter options to WebbPSF docs.
• Add documentation for package level configuration settings
• ttk interface screenshots look worse than the ttk interface actually does these days... time to update them
• Figure out why some :py:meth:'foo' style links (with backticks) won't resolve
• anything to improve for logging functionality docs?
• how to output intermediate step images

[mperrin]

document output mode that only saves the downsampled image, etc.

[mperrin]

Need to document new configuration settings system.

[mperrin]

Much progress in recent commits.

[josePhoenix]

@mperrin: Which of the things you mentioned above are still outstanding, if any? Feel free to edit this checklist.

Moved checklist to initial comment so the progress bar will show up on the issues list page.

[mperrin]

Some updates added. Thanks for organizing this.

[mperrin]

Closed via pull request #33

Thanks for all your efforts cleaning up all these details and generally polishing the presentation - much appreciated.