Add permissive robots.txt
index.html: Don't display link to /contribute on RO site
aboutro.html: make email an email link
Major JavaScript cleanup

- Remove a large chunk of unused code.
- Move summaryTable into census.js, which is the only place it's ever
  used.
- Use protocol-less URLs to refer to 3rd-party libs on a CDN
- Use protocol-less URLs to refer to assets.okfn.org
- Remove recline submodule (unused)