Provide out-of-the-box Wicket portlet support

Wicket portlet-support is coming along quite nicely now (see: WICKET-647).
With the latest changes (see: WICKET-656#action_12525400) WicketPortlet required factory classnames init parameters can now also be provided through a WicketPortlet.properties file defined in the org.apache.wicket.protocol.http.portlet package.
These factory classnames are the only portal specific configurations needed to use Wicket as portlet development framework.
By providing our own WicketPortlet.properties defining our jetspeed specific factory classnames, we can provide Wicket portlet support out-of-the-box, no other configurations needed!

I'll add this properties configuration to our jetspeed-commons project so its available for all applications.