Add a new test for `CreateCtrl`

* I exposed `$controller` service to the closure of the test function.
* I added a function named `testClassCart` which creates a test function for manipulating `classCart` and `storedClassCart`, which encapsulated the old test function.
* I added a new test that tests the functionality that deletes its containing entities which are the entity of `majors` in `classCart` and that of `classes` in `storedClassCart`.