[certiorem] Replace AbstractHubServlet and AbstractSubServlet with jersey resource classes

The jersey project (jersey.dev.java.net) provides support for building REST endpoints and their clients.
The functionality of AbstractHubServlet and AbstractSubServlet can be replaced with equivalent classes annotated with jax-rs annotations.
The advantage of this would be that the resulting classes may be implemented in a servlet container or an embedded container like Grizzly2.
This allows much flexibility in writing unit tests that can start a server and a client and then make client issue requests to the server.

Note that I already have implementation for these classes that have been tested already.

This is not a MUST need right now but I am adding this to keep track of the idea.