code: function(criteria, cb) {
          if (_.isFunction(criteria)) { cb = criteria; criteria = undefined; }
          var self = this;
          var query = buildQuery(criteria);
          client.delete(options(self, query), translateSDKCallback(function (err, data) {
            if (err) { return cb(err); }
            cb(null, data.entities.length);
          }));
        }
docs: destroys (does not retrieve) all entities matching criteria (criteria is optional) returns num of entities deleted to callback