REP-1283 DeRP Filter

I'm not sure if system level tests will be necessary for this story? Since I can actually test the Java filter API doFilter method, my unit tests are fairly comprehensive and can be expanded to cover more cases. Actually, I suppose we need a test for the response messaging service, at least.

Note: The tests won't pass on this branch until we cut a release of http-delegation. We should also probably update the version api-checker uses.
I'm not certain this is the behavior we want. If some one leaves x-delegated out of their whitelist, i could crash through all the security just by providing a bad value in this header with a high quality. It seems to me the more appropriate behavior would be to panic and dump a 500 if we can't parse the header.