stateless ncwms

that chunk of work was starting to get too large and things mostly work, so it's a good time to recap, get some scrutiny, fix things and then continue.

work that was done:
 * remodel TemporalExtent class to be a hash of arrays, each key is a date (stringified) and the array holds moments which are the times of the day
   * all days loaded when ncwms loads
   * times of day are loaded as needed
 * change ui to correspond to those changes
 * modify tests where required

things that don't work:
 * findLayerAsJson is still being called also for ncwms layers, more properties should be taken from the metadata rather than the scanned properties (bounding box etc)
 * next/previous buttons don't work if you move to a day that was not loaded previously - will be fixed
 * make the url which gets the times of the day to have a controller (and also move json parsing logic to be in grails)
Yep, lets do that.

Or if not, I'll discard that commit and something more "standard" will come in my next piece of work. Either.