add new methods for facets: removeFacet, clearFacets, and refreshFacets

src/model.js

@@ -570,7 +570,30 @@ my.Query = Backbone.Model.extend({
     };
     this.set({facets: facets}, {silent: true});
     this.trigger('facet:add', this);
+  },
+  removeFacet: function(fieldId) {
+    var facets = this.get('facets');
+    // Assume id and fieldId should be the same (TODO: this need not be true if we want to add two different type of facets on same field)
+    if (!_.contains(_.keys(facets), fieldId)) {
+      return;
+    }
+    delete facets[fieldId];
+    this.set({facets: facets}, {silent: true});
+    this.trigger('facet:remove', this);
+  },
+  clearFacets: function() {
+    var facets = this.get('facets');
+    _.each(_.keys(facets), function(fieldId) {
+      delete facets[fieldId];
+    });
+    this.trigger('facet:remove', this);
+  },
+  // trigger a facet add; use this to trigger a single event after adding
+  // multiple facets
+  refreshFacets: function() {
+    this.trigger('facet:add', this);
   }
+
 });