Preserve titleMsgId from themesConfig groups

Author: manisandro

src/config_generator/map_viewer_config.py

@@ -371,6 +371,7 @@ def theme_group(self, cfg_group, themes_config, assets_dir, autogenExternalLayer
         self.groupCounter += 1
         group['id'] = "g%d" % self.groupCounter
         group['title'] = cfg_group.get('title')
+        group['titleMsgId'] = cfg_group.get('titleMsgId')
 
         # collect sub theme items
         items = []