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.
> Why should this be True? A comment would be helpful.

To make sure that id is present on the page and it is not an empty. We do it so, because we cannot predict the value of the id (it's generated randomly). I left a comment.