Make off-canvas-list content more easily user-configurable

[leftathome]

We can already customize the URL contents here, but I'm suggesting (not issuing a PR because ... no CCLA still. I don't want to talk about it.) that we just change it to a hash with ChefCorp defaults. "Label": "URL" or "URL": "Label" - dealer's choice.

The hash would be rendering out to the ul tag here: app/views/layouts/application.html.erb#37 (to 43)

... and the ul tag under the "Resources" list on the dashboard here: app/views/pages/dashboard.html.erb#82

I could make my omnibus-supermarket-cookbook wrapper cookbook clobber or rewrite these files on all my app nodes instead but that seems like a really janky way of doing site-specific customizations. Is there already a mechanism/process for doing this documented/demonstrated somewhere in the Supermarket diaspora?

(Also, happy new year.)