Added PartCategory

- Parent can be null (top-level category)
- Parent can be other PartCategory

InvenTree/part/admin.py

@@ -0,0 +1,5 @@
+from django.contrib import admin
+
+from .models import PartCategory
+
+admin.site.register(PartCategory)

InvenTree/part/apps.py

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+from __future__ import unicode_literals
+
+from django.apps import AppConfig
+
+
+class PartConfig(AppConfig):
+    name = 'part'

InvenTree/part/models.py

@@ -0,0 +1,14 @@
+from __future__ import unicode_literals
+
+from django.db import models
+
+class PartCategory(models.Model):
+    name = models.CharField(max_length=128)
+    description = models.CharField(max_length=512)
+    parent = models.ForeignKey('self', on_delete=models.CASCADE, blank=True, null=True)
+    
+    def __str__(self):
+        if self.parent:
+            return str(self.parent) + "/" + self.name
+        else:
+            return self.name

InvenTree/part/tests.py

@@ -0,0 +1,3 @@
+from django.test import TestCase
+
+# Create your tests here.

InvenTree/part/urls.py

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+from django.conf.urls import url
+
+from . import views
+
+urlpatterns = [
+    url(r'^$', views.index, name='index')
+]

InvenTree/part/views.py

@@ -0,0 +1,5 @@
+from django.shortcuts import render
+from django.http import HttpResponse
+
+def index(request):
+    return HttpResponse("Hello world. This is the parts page")