Support regression testing with different Time resolutions

Bugzilla bug 954 addressed support for changing the Time resolution during configuration.

We don't have a way at the moment to systematically change the time resolution for regression tests. That is, we can't force all the tests to run at ps resolution, for example, instead of the ns default.

Possible development steps

• Add a GlobalValue to set the default resolution. (suggest by TomH) (difficulty: 1-2)
• Run all tests with ps resolution, using an environment variable (difficulty: 1)
• Diagnose why individual tests fail (difficulty: 2-3?)
• Systematically support automatic testing of just those tests which should pass (difficulty: 2-4?)