Add some infrastructure for JavaScript-controlled config pages.
This is a port of some of the code in RBCommons used to handle the

admin and My Account pages. It provides some CSS and JavaScript to

display lists of items with optional actions for config pages.
This is, for now, intended to be a subset of the infrastructure used in

RBCommons, and is just enough for the new My Account page. Going

forward, we'll likely extend this for new bits of UI and things like

better dynamic loading of data.

Unit tests pass.
Made use of this with the new My Account page.