Migrate InvenTreeTree to using MPTT model

InvenTree/part/migrations/0019_auto_20190908_0404.py

@@ -0,0 +1,37 @@
+# Generated by Django 2.2.5 on 2019-09-08 04:04
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0018_auto_20190907_0941'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='partcategory',
+            name='level',
+            field=models.PositiveIntegerField(default=0, editable=False),
+            preserve_default=False,
+        ),
+        migrations.AddField(
+            model_name='partcategory',
+            name='lft',
+            field=models.PositiveIntegerField(default=0, editable=False),
+            preserve_default=False,
+        ),
+        migrations.AddField(
+            model_name='partcategory',
+            name='rght',
+            field=models.PositiveIntegerField(default=0, editable=False),
+            preserve_default=False,
+        ),
+        migrations.AddField(
+            model_name='partcategory',
+            name='tree_id',
+            field=models.PositiveIntegerField(db_index=True, default=0, editable=False),
+            preserve_default=False,
+        ),
+    ]

InvenTree/part/migrations/0020_auto_20190908_0404.py

@@ -0,0 +1,21 @@
+# Generated by Django 2.2.5 on 2019-09-08 04:04
+
+from django.db import migrations
+from part import models
+
+
+def update_tree(apps, schema_editor):
+    # Update the PartCategory MPTT model
+
+    models.PartCategory.objects.rebuild()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0019_auto_20190908_0404'),
+    ]
+
+    operations = [
+        migrations.RunPython(update_tree)
+    ]