Couple of API tweaks for work orders

made a change to sorting such that it assumes the primary model is
being sorted, if caller does not specify

tailbone/api/workorders.py

@@ -66,6 +66,12 @@ class WorkOrderView(APIMasterView):
             'date_delivered': six.text_type(workorder.date_delivered or ''),
         }
 
+    def create_object(self, data):
+
+        # invoke the handler instead of normal API CRUD logic
+        workorder = self.workorder_handler.make_workorder(self.Session(), **data)
+        return workorder
+
     def update_object(self, workorder, data):
         date_fields = [
             'date_submitted',
@@ -79,7 +85,7 @@ class WorkOrderView(APIMasterView):
             if field in data:
                 if data[field] == '':
                     data[field] = None
-                else:
+                elif not isinstance(data[field], datetime.date):
                     date = datetime.datetime.strptime(data[field], '%Y-%m-%d').date()
                     data[field] = date