Complete build now works

- Marks build as complete
- Deletes temporary BuildItem objects
- Preselects the part's default_location if there is one
- Creates a new stockitem in the selected location

InvenTree/stock/migrations/0010_auto_20190501_2344.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2 on 2019-05-01 13:44
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stock', '0009_auto_20190428_0841'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='stockitem',
+            name='batch',
+            field=models.CharField(blank=True, help_text='Batch code for this stock item', max_length=100, null=True),
+        ),
+    ]

InvenTree/stock/models.py

@@ -158,7 +158,7 @@ class StockItem(models.Model):
     URL = models.URLField(max_length=125, blank=True)
 
     # Optional batch information
-    batch = models.CharField(max_length=100, blank=True,
+    batch = models.CharField(max_length=100, blank=True, null=True,
                              help_text='Batch code for this stock item')
 
     # If this part was produced by a build, point to that build here