Proposed change to allow `JHtml::_('bootstrap.loadCss')` usage auto detect language direction

gistfile1.php

/**
	 * Loads CSS files needed by Bootstrap
	 *
	 * @param   boolean  $includeMainCss  If true, main bootstrap.css files are loaded
	 * @param   string   $direction       rtl or ltr direction. If empty, ltr is assumed
	 * @param   array    $attribs         Optional array of attributes to be passed to JHtml::_('stylesheet')
	 *
	 * @return  void
	 *
	 * @since   3.0
	 */
	public static function loadCss($includeMainCss = true, $direction = NULL, $attribs = array())
	{
		// Load Bootstrap main CSS
		if ($includeMainCss)
		{
			JHtml::_('stylesheet', 'jui/bootstrap.min.css', $attribs, true);
			JHtml::_('stylesheet', 'jui/bootstrap-responsive.min.css', $attribs, true);
			JHtml::_('stylesheet', 'jui/bootstrap-extended.css', $attribs, true);
		}

		// Load Bootstrap RTL CSS
		if ($direction == 'rtl' || ($direction = NULL && JFactory::getDocument()->direction == 'rtl'))
		{
			JHtml::_('stylesheet', 'jui/bootstrap-rtl.css', $attribs, true);
		}
	}