Set the fieldgroup_id when you associate and dis-associate
Merge branch 'feature/fields_refactor' of github.com:globaleaks/GlobaLeaks into feature/fields_refactor

* 'feature/fields_refactor' of github.com:globaleaks/GlobaLeaks:
  fixed exception due to unitialized variable
Merge branch 'feature/fields_refactor' of github.com:globaleaks/GlobaLeaks into feature/fields_refactor

* 'feature/fields_refactor' of github.com:globaleaks/GlobaLeaks:
  fixed bug related to field gration from template