Edit group configurations.

Ticket: [BLD-1067](https://openedx.atlassian.net/browse/BLD-1067)

**Acceptance criteria:**
* Edit link from Group Configurations page for each group configuration.
* Do not surface group information nor allow groups to be edited (will be a separate story). 

**sandbox:** http://studio.polesye.m.sandbox.edx.org/

@andy-armstrong , @frrrances , @cahrens , @explorerleslie, @mhoeber  please review.
> If you had the ID's in the expected response, you wouldn't need to call _remove_ids. Why are you removing the group ID's?
> 
> I am guessing it is because of the random ID on the group configuration. But here you know what all the IDs should be-- they are in expected.

Fixed.