clone cms with menus, make menus standalone app

cms/cms_plugins.py

@@ -0,0 +1,19 @@
+from django.utils.translation import gettext_lazy as _
+
+from cms.models.placeholderpluginmodel import PlaceholderReference
+from cms.plugin_base import CMSPluginBase
+from cms.plugin_pool import plugin_pool
+
+
+class PlaceholderPlugin(CMSPluginBase):
+    name = _("Placeholder")
+    parent_classes = ['0']  # so you will not be able to add it something
+    # require_parent = True
+    render_plugin = False
+    admin_preview = False
+    system = True
+
+    model = PlaceholderReference
+
+
+plugin_pool.register_plugin(PlaceholderPlugin)