Refactor

As all points from the epic refactor issue are closed #47 (closed) I am merging this in to master in order to unblock development.

backend/core/admin.py

 from django.contrib import admin
+from django.contrib.auth.models import Group
 
-from .models import Feedback, Student, Submission, SubmissionType, Test
-
-# Register your models here.
+from core.models import (ExamType, Feedback, Reviewer, Student, Submission,
+                         SubmissionType, Test, Tutor, UserAccount)
 
+# Stuff we needwant
+admin.site.register(UserAccount)
 admin.site.register(SubmissionType)
 admin.site.register(Feedback)
-admin.site.register(Student)
 admin.site.register(Test)
+admin.site.register(ExamType)
 admin.site.register(Submission)
+admin.site.register(Reviewer)
+admin.site.register(Student)
+admin.site.register(Tutor)
+
+# ... and stuff we don't needwant
+admin.site.unregister(Group)