D 17479 cnorm filter

This modifies the behavior of the Accept header.

Now it is much more strict:
* If there's an accept header that matches any in the list of acceptable headers, it's used
* If none of the accept headers match any in the list, the preferred one is used
* If no accept header is specified, the preferred one is used
* It takes out any "quality" or additional garbage tacked on to the accept header: `derp/xml;q=.1`

It will no longer throw NPEs when one or the other (or neither!) of the configs are specified for this filter. Which means you could potentially configure an empty filter that does nothing, but that's silly.