REP-1283 DeRP Filter

This one was actually quite fun. I got to draw state machines and translate them into a regular expression. I got to code against the actual Java servlet API rather than using the Repose specific API. I got to play some more with Java/Scala integration. Good times.

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.

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.
Is this the same performance concern as the regexp?