Remove user_partitions from advanced settings

**Ticket:** [BLD-1091](https://openedx.atlassian.net/browse/BLD-1091)

* Add user_partitions to filter list (list of settings NOT shown in Advanced Settings).
* Advanced settings page should no longer list have the user_partitions setting. 

**sandbox:** http://studio.auraz.m.sandbox.edx.org/

@andy-armstrong , @cahrens , @mhoeber , @explorerleslie please review.