Sets the baseUrl property.
This property is made up of scheme, host and base_path, e.g. 'http://www.example.com/mydrupalinstall/'
The base url is usually set by the request but we allow it to be set independent of the request so that code that calls url() outside the context of a request can use the global $base_url variable to set this value.
@todo Remove this once the url() function no longer supports being called when there is no request.
The base url to use for url generation.
public function setBaseUrl($url);