Housekeeping on LaTEX and EPUB output

[k4kfh]

While we technically have LaTEX and EPUB output set up with ReadTheDocs, there are a handful of things I'd like to see done to make it more official.

• Configure Sphinx to insert the full text of the license at the end of the LaTEX and EPUB output (without adding a page to the HTML site)
• Configure Sphinx to add a footer with the license on all pages of the LaTEX and EPUB output. It's already set up to do this on the HTML site.
• Add a preamble to LaTEX and EPUB output telling the user that this documentation is auto-generated with Sphinx/ReadTheDocs, with a link to this repository. Recommend submitting a GitHub issue if any error is found.