QmlDesigner.PropertyEditor: Bringing back checkbox for TR

Change-Id: I350b8d8fa6c59a48d4a89935ed40c8cff028beaf
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
QmlDesigner.PropertyEditor: fix label

Change-Id: Ibf92f565f9b33f5739bb3e0a19920f160c0b44f7
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>