Convert Config entity to use "id" instead of "@group"

Summary:
* this syncs the config entity API with backend changes introduced by D472 (243a2ffbe75fc1e9bed3fcea319a855d1735c98f)
* change
  * the endpoint services
  * the mock data for map config

Test Plan: * check if config pages behave correctly

Reviewers: shadowhand

Reviewed By: shadowhand

Subscribers: rjmackay, seth, aMoniker

Maniphest Tasks: T849

Differential Revision: https://phabricator.ushahidi.com/D496