Various YUIDoc uptates for the Test module

This PR only updates various YUIDoc blocks across the Test module.

- [x] Removes namespace notation based on the feedback from @rgrove. I didn't update the whole module but the assertion classes only. This is done in separate commits that I can abandon if you're not happy with that change.
- [x] Updates notation for optional parameters
- [x] Add various usage examples where I thought some clarification would be helpful
- [x] Fix #1479