Corrected type of property _currentRoute

The (name) matched route is stored in the _currentRoute property (https://github.com/zendframework/zf1/blob/master/library/Zend/Controller/Router/Rewrite.php#L400), which is a string. It can then be retrieved using getCurrentRoute() which returns the route interface. Renaming the _currentRoute property to _currentRouteName would be a BC-break.