Enrollment API Cleanup

This PR will capture the following work
* Update to version 1
* Change URL scheme to match other APIs
* Add Course Enrollment Detail entry point
* Use Class Based DRF views

@ormsbee @wedaly This should be ready for review. 

CourseEnrollmentException is the root error for all model updates from the student models. This was actually a mistake on my part. What I wanted to is catch these exceptions at the data layer and push a CourseEnrollmentError from the api.py layer