Don't save any App Settings for which value would not change

that lets us avoid writing "redundant" values to the database, whereas in fact
the underlying value may be coming from config file

tailbone/templates/appsettings.mako

@@ -1,7 +1,7 @@
 ## -*- coding: utf-8; -*-
 <%inherit file="/base.mako" />
 
-<%def name="title()">${self.app_title()} App Settings</%def>
+<%def name="title()">App Settings</%def>
 
 <%def name="content_title()"></%def>
 

tailbone/views/settings.py

@@ -180,6 +180,8 @@ class AppSettingsView(View):
         return self.rattail_config.get(setting.namespace, setting.name, default='')
 
     def save_setting_value(self, setting, value):
+        existing = self.get_setting_value(setting)
+        if existing != value:
             legacy_name = '{}.{}'.format(setting.namespace, setting.name)
             if setting.data_type is bool:
                 api.save_setting(Session(), legacy_name, 'true' if value else 'false')