(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 It will be superseded by the `:follow-redirects` option if both are set at the same time.
What happens if the scheme on the redirect is different than on the request, e.g., originally the request went to *http://target/blah* but was redirected to *https://target/blah*?  Would the port change from 80 to 443 so this condition is caught or would it be -1 on both and, therefore, potentially leading to munging to the wrong location?