[#145,widget/fields,model][m]: working fields widget with field summary data generated by Dataset.getFieldsSummary function.

* Layout is still not right -- need to put widget in sidebar (though looks a lot better)
* Datset.getFieldsSummary to compute facets for fields
* Remove facet usage in the demo

app/js/app.js

@@ -242,7 +242,6 @@ var ExplorerApp = Backbone.View.extend({
 // provide a demonstration in memory dataset
 function localDataset() {
   var dataset = Fixture.getDataset();
-  dataset.queryState.addFacet('country');
   return dataset;
 }