Add routing support for variables in end point URI paths

[Mihael Schmidt]

Currently only fixed paths are supported by the router module like

/mdm/item

But in REST you normal like to add the document id to the path like

/mdm/item/5500

But as the id is dynamic/variable this won't work with the current routing strategy (longest matching path).

We need to introduce variables to the path like

/mdm/item/{id}

The variable should be named as we can later query it by index or by name (though this is not part of this issue).