Issue 271: Standardize the way state is reset between test cases

[kmanning]

• Issue Testing: Cleanup Test resets #271
• If you have global state that needs to be modified as part of your test, you need to clean that up, or it may affect future tests
• Let's create a simple and consistent way to do so
  • For your class that has global state, create a static reset method to do so, and implement the Resettable interface.
  • For your test, use the ResetStaticStateExtension - this will automatically run reset on all Resettable classes with a @beforeeach and @AfterEach.