catalog-backend: wrap location-specific rules in an additional rules field

docs/features/software-catalog/configuration.md

@@ -37,7 +37,8 @@ catalog:
   locations:
     - type: github
       target: https://github.com/org/example/blob/master/org-data.yaml
-      allow: [Group]
+      rules:
+        - allow: [Group]
 ```
 
 We are able to add entities of kind `Component`, `API`, or `Template` from any

docs/features/software-templates/adding-templates.md

@@ -67,7 +67,8 @@ catalog:
   locations:
     - type: github
       target: https://github.com/spotify/cookiecutter-golang/blob/master/template.yaml
-      allow: [Template]
+      rules:
+        - allow: [Template]
 ```
 
 Templates can also be added by posting the to the catalog directly. Note that if