Add feature demo for importing Square transactions to CORE-POS

also allow delete of CORE-POS transactions, for sake of demo

rattail_demo/web/templates/corepos/transaction-details/index.mako

@@ -0,0 +1,11 @@
+## -*- coding: utf-8; -*-
+<%inherit file="/master/index.mako" />
+
+<%def name="context_menu_items()">
+  ${parent.context_menu_items()}
+  % if request.has_perm('{}.import_file'.format(permission_prefix)):
+      <li>${h.link_to("Import {} from Square CSV".format(model_title_plural), url('{}.import_square'.format(route_prefix)))}</li>
+  % endif
+</%def>
+
+${parent.body()}