3.0 helper

- Removed $confirmMessage param from FormHelper::postLink() and HtmlHelper::link(). It can be set using "confirm" key in $options.
- Documented "default" option for HtmlHelper::link(). Though personally I would like to get rid of it. Preventing the default redirection behavior of link by itself isn't very useful. You would have some associated js to do something useful in which case the default behavior preventing can be taken care of by the extra js code itself.