GUI: Fixed display of sync status of groups

- Value in "synchronizationEnabled" attribute is String, so we can't
  just return value from attribute as JSNI boolean. It was wrong in
  conditions but correct on debug message.
- Added some null checks when processing RichGroups.
- Source format of JsonUtils.
Merge pull request #625 from zlamalp/sync

GUI: Fixed display of sync status of groups