Consolidated all Jersey*Resources into a single HttpResource class.

Less code, less complexity, and a better reflection of how HTTP works.
Fixed issues with response closing and subscription chaining.

1. Under certain circumstances, responses could be leaked.
2. Composite subscriptions were not correctly maintained.
Implemented asynchronous behavior in a more conventional way.

Previously, we accessed the Client's ExecutorService directly, and scheduled our own tasks there. Now, we use AsyncResources to schedule tasks for us, and ITypeListener to hand off to Observers.