Add initial Shopfoo pattern feature

data models, import/export, web views etc.

rattail_demo/db/model/__init__.py

@@ -0,0 +1,13 @@
+# -*- coding: utf-8; -*-
+"""
+Rattail Demo data model
+"""
+
+# bring in all the normal stuff from Rattail
+from rattail.db.model import *
+
+# also bring in CORE integration models
+from rattail_corepos.db.model import *
+
+# now bring in Demo-specific models
+from .shopfoo import ShopfooProduct, ShopfooProductExport