Extract query / facets extraction to interface implentation

[Haehnchen]

We have implemented an encode / decoder pattern for facet extraction of out the requests. This allows us to switch directly between your psr-7 parser and a Symfony form submit request

for example we replaced:

    public function getSelectedValues(UriInterface $uri)
    {
        $queryParams = Psr7\parse_query($uri->getQuery());