Add the given items to the given queue. For each item, also add the given extraParams.
@param {Array} items the items to add to the queue
@param {Object} extraParams extra data that should be added to each item
@param {MongodbQueue} targetQueue the queue to push the messages to
@param {Function} cb the callback function
function addToQueue(items, extraParams, targetQueue, cb) {
  if (!items || items.length === 0) {
    return cb();
  }
  var itemsToPush = _.map(items, function(item) {
    return _.extend({}, item, extraParams);
  });
  debug("adding %d items to queue %s", itemsToPush.length, targetQueue.getName());
  targetQueue.addMany(itemsToPush, cb);
}