validation messages in tooltips

Implementation of two kind presentation of validation messages:
- in tooltips 
- in p-tag under the input field

In both case validation message disappear on click, keydown, change and blur events of invalid input.

PS I think ParametrizedFunction is useful class and should be moved into wicket-jquery-selectors (I wrote the todo in javadoc).
do we want to add empty attribute values at all ?