Add pandoc pagebreak filter
Add a custom PDF footer with phantomjs
Add some extra html markup via javascript.

In order to style up some elements for pdf generation, it’s necessary
to add some spans via javascript. Some of this can be fixed by
modifying lesson markdown / manifests, but it’s perhaps simplest to
do it this way.
Add a legend template; move it into position in js

[partial. Requires some css]
Lots of new print styles!