Invalidate cache when a location is changed

[adieyal]

1. Edit the name of a location in the admin suite
2. Load up the api, e.g. https://production.wazimap-ng.openup.org.za/api/v1/profile/8/points/category/394/points/?format=json

Notice that the name hasn't changed

3. Hard refresh

The name has now updated

The cache should be invalidated on save

0.12

https://trello.com/c/XN45Ltdg/612-invalidate-cache-when-a-location-is-changed