(PDB-772) Modify the facts endpoint to return structured facts

This pull request causes the v4 facts endpoint to return typed and structured
facts while leaving the v3 responses stringified as before.  It also adds a
"name" column to the fact_paths table representing the first element of a
fact's path.  This column should be renamed to "fact" in the future to avoid
confusion with the many references to 'certname' as name.
I think we should just use the emacs defaults, if for no other reason than it's trivial to use them to automate bulk-reformatting of our stuff. I prefer to settle all style debates with tools that auto-enforce the style (a la gofmt). :)