Added BuildItemAllocation Model

- Used to link stock items to a build

InvenTree/build/migrations/0003_builditemallocation.py

@@ -0,0 +1,25 @@
+# Generated by Django 2.2 on 2019-04-29 12:14
+
+import django.core.validators
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stock', '0009_auto_20190428_0841'),
+        ('build', '0002_auto_20190412_2030'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='BuildItemAllocation',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('quantity', models.PositiveIntegerField(default=1, help_text='Stock quantity to allocate to build', validators=[django.core.validators.MinValueValidator(1)])),
+                ('build', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='allocated_stock', to='build.Build')),
+                ('stock', models.ForeignKey(help_text='Stock Item to allocate to build', on_delete=django.db.models.deletion.CASCADE, related_name='allocations', to='stock.StockItem')),
+            ],
+        ),
+    ]

InvenTree/build/migrations/0004_build_url.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2 on 2019-04-29 12:18
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('build', '0003_builditemallocation'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='build',
+            name='URL',
+            field=models.URLField(blank=True, help_text='Link to external URL'),
+        ),
+    ]