Better programmatic configuration.

- Dispatcher servlets and their contexts are now easier to configure.

- Moved all resources to test directories to better reflect real-world use cases.

- Added tests that start up Jetty and used retrofit to make a sequence of API calls.

- Fixed bug in rhizome utils that was causing unhappiness when a configuration was not found.

- Fixed bug in rhizome configuration service that was prevent configurations from being properly updated.

- Added toString method for simple configuration key.

- Added JacksonConverter based on square retrofit converter, but with some additional handling for null bodies.