Locking down some test terminology

Hi all,

Before I write up the findings of the existing test management software, I
wanted to lock down some terminology. Here is a first pass at describing
the aspects of a test that are particularly important for the test harness
we are prototyping: Test Harness and Test vocabulary
<https://github.com/w3c/aria-at/wiki/Test-Harness-and-Test-vocabulary>

Please check it out, and feel free to expand or offer different terms!

Valerie