First stab at images and git-annex.

Let's add a photo and some filters to produce a handy little image
information page.

It's not so nice to store these (relatively) huge files in git, so we'll
store them in git-annex and update the deployment scripts to handle it.

Nothing links to this image yet as this is pushed mainly to validate the
git-annex deployment, but it will be accessible by direct URI.

The intention is that the site should still compile with missing annexed
components, just that those items will be missing.  In the future we could
perhaps replace them with stubs (so at least the description part of the
info page would work) but we'll save that activity for another day.