Make Wagn skinnable+issues

Wagn's appearance is extremely flexible, but making use of that flexibility requires diving into CSS. We'd like to offer at least one intermediate layer in which people can choose among skins that have been developed by working with CSS, and perhaps another layer that lets Editors/Wagneers build a skin, or at least tweak existing ones.

Minor issues that would be helpful (not really about the ticket title - break out to other ideas/tickets?):

1. *navbox being horizontally narrow - width is set by default to 30% of its enclosing div (which is the full top bar for the regular menu, and the card-slot for others).
2. add some interface around draggable pointers - icon to the left of the text box? In the long run I imagine being able to drag around items from view-mode Pointers, so perhaps should harmonize with look of card title bars.