Renamed 'customer-order' app to 'customer'

- This app should manage more than just orders
- Moved the 'Customer' model into this app

InvenTree/stock/migrations/0013_auto_20180417_1337.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.12 on 2018-04-17 13:37
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stock', '0012_auto_20180417_1316'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='stockitem',
+            name='customer',
+            field=models.ForeignKey(blank=True, help_text='Item assigned to customer?', null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='stockitems', to='customer.Customer'),
+        ),
+    ]