First attempt to services section

- base.py: add settings to load GlasfaserServicesPlugin by default
    - glasfaser_cms_page.html: create a placeholder for services
    - cms_plugins.py: add the plugin code
    - models.py: add UngelichTextSectionWithImage model

dynamicweb/settings/base.py

@@ -321,6 +321,15 @@ CMS_PLACEHOLDER_CONF = {
             },
         ]
     },
+    'glasfaser_services': {
+        'name': "Services",
+        'plugins': ['GlasfaserServicesPlugin'],
+        'default_plugins': [
+            {
+                'plugin_type': 'GlasfaserServicesPlugin',
+            },
+        ]
+    },
 }
 
 CACHES = {