Performance benchmarks that use the JCR API

We need the ability to run a series of performance benchmarks against different versions of ModeShape (as well as other JCR implementations, such as the reference implementation). The tests should use only the JCR API. Once the framework has been completed, it should be easy to add more tests; the framework should run each test multiple times and (ideally) report the five-number summary for each test against each repository. This would allow us to track the trends in performance for our releases, and to compare the performance of ModeShape to other implementations.

We already have a connector benchmark module (under "utils" folder in the codebase) that generates graphs (though not five-number), so this could be adapted.