Add arguments to cre endpoint to support the standard integration and metrics

[Rob van der Veer]

When a standard like WSTG links to OpenCRE's, we at least can ask them to add an argument saying 'source=bla' where bla needs to be some recognizable name for the standard - perhaps an encoded name, or something else that may be less likely to change over time.
That way we can keep count.
Also: do we need more info that will help us in parsing? I guess not because for WSTG we'll use the content of the page to parse the title and reconstruct the hyperlink, right?