Extend cpn:link tag to add selectors, parameters etc.

[stoerr]

The cpn:link tag could be enhanced with more attributes to match, even extend the sling:include functionality of addSelectors, replaceSelectors, replaceSuffix etc. and thus make the functionality of SlingUrl available in a good way to JSPs.

We could add the attributes addSelectors, replaceSelectors, (removeSelectors), replaceSuffix, replaceExtension, addParameter (a little unclear how to represent both value and key here), replaceFragment. Possibly replacePathAndName (for full URLs).

There also could be a attribute resource as an alternative to href with a Resource value, and very possibly for that case a boolean map attribute for mapped / unmapped URLs.