Allow testName and tags to be set globally or overridden by browser configs

This restores the ability to set tags for tests, which can be done as part of the top level config or as a property on each browser config object.

This also allows overriding `testName` with a `name` property on the browser config object.

Lastly, and somewhat tangentially, I changed the `Job` constructor to accept the `TestRunner` instance itself, so it can pull off the properties it needs and be less prone to changes that may happen in the future. I made this change hesitantly, and if you'd like me to remove it I will.