Clean up c object

[bellisk]

This PR was initially just to pass in the search_facets parameter into the facet_list.html template, as it's now required. Then I got the idea of cleaning up the old c object from the templates too.

@pdelboca Do I have it right that we should be passing these extra variables along as extra_vars and not adding them to the g object, in the views? I didn't change that yet, but I can also clean up the places where we add to the g object there as well.