[TASK] Allow and replace special characters like umlauts

Currently ``<v:format.uri.sanitizeString />`` strips all special characters like umlauts which is not what one would expect. Open for discussion though is if this feature should be configurable via viewhelper argument.
Buddy, there's a lib for that: https://github.com/cocur/slugify/blob/master/src/Slugify.php mind copying?