Make the Course Structure admin slightly more usable (list/search fields)

openedx/core/djangoapps/content/course_structures/admin.py

+import json
+
 from ratelimitbackend import admin
 
 from .models import CourseStructure
 
-admin.site.register(CourseStructure)
+class CourseStructureAdmin(admin.ModelAdmin):
+    search_fields = ('course_id', 'version')
+    list_display = (
+        'id', 'course_id', 'version', 'created'
+    )
+    list_display_links = ('id', 'course_id')
+
+admin.site.register(CourseStructure, CourseStructureAdmin)