WL-98 As a course instructor, auto-register (as well as auto enroll) a list of students into my course

@chrisndodge here are the changes related to WL-98 for your quick reivew. 
we have written the test cases but only one coverage is missing in our code.  
currently we did not check/test the code for quality.

In order to test this feature you need to set the flag: 
FEATURES['ALLOW_AUTOMATED_SIGNEDUPS'] = True
@cahrens actually here we are trying to handle the exceptions that can be raised during account creation and enrollment procedure, exceptions like NonExistentCourseError, CourseEnrollmentException, EnrollmentClosedError, CourseFullError, AlreadyEnrolledError etc etc. 
so here we are explicitly raising one of those exceptions. 
however if we post with invalid course ID then code flow will handle this exception at the earlier stage.