doc: Re-indent makefiles slightly.
doc: Add script for saving local copy of assets.

When building for the server, use "make serverhtml" instead, which
specifies links to CDN, etc.
doc: Reinstate custom CSS.

The following styles were not included:
 * Remove several 'pre' stylings which are done by the Bootstrap theme.
 * Remove 'table.docutils' styling. Bootstrap's style appear adequate,
   and this doesn't work anyway since the 'docutils' class is removed by
   some JS.
 * Remove 'margin-top' on 'table.hlist td ul'. All 'ul' are reset by
   Bootstrap already.
doc: Use epigraph for quotes.
doc: Bootstrap-ify the overview page.

It should be more responsive now, and have a couple things better
aligned, too.
doc: Remove sidebar from index pages.

The ToC doesn't seem to be generated for these pages, so just disable it
for now.
doc: Remove some unintentional blockquotes.

I may have introduced a few of these when I didn't understand reST
syntax as well. This was not a problem with the default theme, but on
bootstrap, the blockquote appears out of place.