Specify order of test execution

I would probably offer 4 options for ordering:

• Default (leave to the test framework - this is usually alphabetical)
• Alphabetical
• Declaration
• Randomized (different for each run)

However overriding the order could decrease performance though, as I would need to call the executor per test (as to avoid it reordering the tests). I will need to test how significant this could be. I could also add test framework specific order control, but that is more work.