Djblets now provides a djblets-js-tests bundle containing all JavaScript

unit tests. This currently consists only of the configForms tests.

Consumers can include this bundle along with their own tests bundles.
While integrating this, I found issues with the configForms tests. The

icon tests weren't passing, due to changes to how icons were

represented. I also noticed that we were still prefixing icon names with

rb-icon-, which wasn't ideal. We now default to djblets-icon-, but

callers can override this by overriding iconBaseClassName.

Integrated these tests in Review Board. They passed.