Closeable on Bench Sub-objects is Confusing

[stanbrub]

The Bench class, which is not AutoCloseable contains builder objects that are. This is inconsistent. Any usage of a Bench instance through the builder pattern should not expose sub-objects in such a way that they can be closed without calling the close on the Bench instance. This is not currently a major issue.

• Have sub-object implement a local interface that provides close, and possibly other common methods, instead of Closeable.
• Allow the Bench class to be AutoCloseable (saves a few lines of code in some cases)