Add migration for new overrides table

lms/djangoapps/grades/migrations/0013_persistentsubsectiongradeoverride.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('grades', '0012_computegradessetting'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='PersistentSubsectionGradeOverride',
+            fields=[
+                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
+                ('created', models.DateTimeField(auto_now_add=True, db_index=True)),
+                ('modified', models.DateTimeField(auto_now=True, db_index=True)),
+                ('earned_all_override', models.FloatField(null=True, blank=True)),
+                ('possible_all_override', models.FloatField(null=True, blank=True)),
+                ('earned_graded_override', models.FloatField(null=True, blank=True)),
+                ('possible_graded_override', models.FloatField(null=True, blank=True)),
+                ('grade', models.OneToOneField(related_name='override', to='grades.PersistentSubsectionGrade')),
+            ],
+        ),
+    ]