AME-9016 Update Karma to use Mocha Reporter

Replace QUnit with Karma/Mocha/Chai Karma provides a web server for hosting the tests, which removes the requirement for an application server to deploy to. This makes it possible to easily integrate the unit tests into the build. It also watches the source files and automatically reruns the tests. Mocha and Chai provide a modern testing experience, with a BDD testing style and comprehensive assertions. As part of this change, the QUnit tests that were functional-style tests have been removed. The plan is to eventually replace them with true functional Selenium tests.