Add new views for App Info, and Configure App

and a way to specify version/url overrides for buefy, vue etc.

also, begin logic for "standard" admin menu

tailbone/views/master.py

@@ -2248,6 +2248,8 @@ class MasterView(View):
         route = self.get_route_prefix()
         return self.request.route_url(route, **kwargs)
 
+    # TODO: this should not be class method, if possible
+    # (pretty sure overriding as instance method works fine)
     @classmethod
     def get_index_title(cls):
         """
@@ -4822,6 +4824,8 @@ class MasterView(View):
                     value = six.text_type(bool(value)).lower()
                 elif simple.get('type') is int:
                     value = six.text_type(int(value or '0'))
+                elif value is None:
+                    value = ''
                 else:
                     value = six.text_type(value)