Update error on change

Fixed the problem where input errors are never updated when 'update_on' is set to 'change' in the config.

When 'update_on' is set to 'change', there are still some validations performed on 'keyup'.
The 'keyup' validations are done silent and thus do not trigger an error message on the element.
The 'keyup' validations remove the 'changed'-flag and prevent the 'onchange' event to be fired.

By adding a new key to the element model ('validationSilency') the 'onchange' event is fired when we do a 'change' event after a 'keyup' event.