Major revisions to replace TestClass context with test runner context

• MethodWatcher: Add runner argument to methods to provide context.
• RunWatcher: Revise methods to replace TestClass/method context with AtomicTest.
• Replace deprecated TestClassWatcher interface with TestClassWatcher2.
• UnitTestWatcher: Update bases on MethodWatcher revisions.
• Replace remaining uses of TestClass as context with runner object.
• Add code to track the active test runner of each thread.
• RunReflectiveCall: Only try to retrieve runner for "particle" methods.
• Configure unit tests to run in parallel.
• Update README to document current API.