Stateless ncwms get filters as json

 * Stateless `getFiltersAsJSON controller for ncwms
 * Stateless `getStylesAsJSON controller for ncwms
 * Client parsing is now much dumber
 * Date assembly is done in server side (grails)

This API is still work in progress, but enables us to see where we actually want to get to.
I'll address this but in a different PR, I think something else introduced this delay.