QmlJS: QmlDesigner warnings should be warnings

Task-number: QTCREATORBUG-10898
Change-Id: I6d8a1b1523d72950fad25eb8545c24085552b226
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>
QmlDesigner.PropertyEditor: TextField "Delete" should not delete items

Change-Id: I7434d1d9f8175cf2799ea4eea491cdcbaee40040
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>