change 'index' resource query parameter to 'parameters' to match Services

Services defines its various 'index' type resources to take the query parameters in a query parameter named 'parameters':

            array(
              'name' => 'parameters',
              'optional' => TRUE,
              'type' => 'array',
              'description' => 'Parameters array',
              'default value' => array(),
              'source' => array('param' => 'parameters'),
            ),

Meanwhile, we use 'params':

        array(
          'name' => 'parameters',
          'optional' => TRUE,
          'type' => 'array',
          'description' => 'Filter parameters array such as param[title]="test"',
          'default value' => array(),
          'source' => array('param' => 'param'),
        ),

This is an avoidable confusion. Let's change ours.