Remove expected exception

The commits to this branch so far remove all use of "advanced" capabilities of ExpectedException from the NUnit tests, with the exception <g> of our own tests _of_ those capabilities. This includes:
* IExceptionHandler interface
* Alternate handlers
* Message tests

All of our usage has been replaced by Assert.Throws or Assert.That with a ThrowsConstraint.

Once this is merged in, the next phase will be to remove all remaining use of ExpectedException, again excluding our own tests of ExpectedException.

The final phase will be to remove all or part of ExpectedException as a feature, depending on what decisions come out of  the currently ongoing discussion.