Implemented bidirectional traversal for PART and STOCK apps

- Added list view for StockItems

InvenTree/stock/views.py

@@ -0,0 +1,43 @@
+from django.http import HttpResponse
+from django.template import loader
+
+from django.shortcuts import get_object_or_404, render
+
+from .models import StockItem, StockLocation
+
+def index(request):
+    template = loader.get_template('stock/index.html')
+
+    items = StockItem.objects.all()
+
+    location = None
+
+    if 'location' in request.GET:
+        loc_id = request.GET['location']
+
+        location = get_object_or_404(StockLocation, pk=loc_id)
+
+        items = items.filter(location = loc_id)
+
+        children = StockLocation.objects.filter(parent = loc_id)
+
+    else:
+        # No stock items can exist without a location
+        items = None
+        location = None
+        children = StockLocation.objects.filter(parent__isnull=True)
+
+    context = {
+        'items' : items,
+        'location' : location,
+        'children' : children,
+    }
+
+    return HttpResponse(template.render(context, request))
+
+
+def detail(request, pk):
+
+    item = get_object_or_404(Stock, pk=pk)
+
+    return render(request, 'stock/detail.html', {'item' : item})