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.
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