(TK-33) Add support for location header munging on a proxied redirect

This PR adds an option to munge the location headers on redirect responses received by a proxy servlet. This option can be set in the options passed into the `add-proxy-route` function. It will be superseded by the `:follow-redirects` option if both are set at the same time.
I think it might be better to phrase the message as "unsupported" rather than "incorrect".  Also, for easier troubleshooting, might be nice to itemize this error to say which one was -- or ones were -- unsupported.