MBS-799/MBS-5920: don't allow area annotation or alias editing for non-location-editors
MBS-799/MBS-5920: don't show links that should not be usable to non-location-editors
MBS-799/MBS-5920: disallow editing of relationships that should not be editable by non-location-editors
MBS-799/MBS-5920: rewrite Data::Relationship->editor_can_edit for clarity
MBS-799/MBS-5920: factor out editor_can_edit checks in Controller::Edit::Relationship
Merge branch 'areas-limit-appropriately'

* areas-limit-appropriately:
  MBS-799/MBS-5920: factor out editor_can_edit checks in Controller::Edit::Relationship
  MBS-799/MBS-5920: rewrite Data::Relationship->editor_can_edit for clarity
  MBS-799/MBS-5920: disallow editing of relationships that should not be editable by non-location-editors
  MBS-799/MBS-5920: don't show links that should not be usable to non-location-editors
  MBS-799/MBS-5920: don't allow area annotation or alias editing for non-location-editors