code: function list (req, modelName, callback) {
      return get(modelName, true).getList(req, callback);
  }
docs: Retrieve the list DSL for a model
  @param  {Object}   req       A HTTP request object which can be used to customised the list
  @param  {String}   modelName The name of the model
  @param  {Function} callback  A callback to return the list DSL to
  @return {Void}