New Wicket Portlet support

I'm providing a new solution for Wicket Portlet support, see also my initial proposal on the wicket-dev list: http://www.nabble.com/A-new-proposal-for-Wicket-Portlet-support-tf3836652.html

As this solution will require a few (but not very much) changes to Wicket core, I'll create a separate branch first to let everyone involved review and test it out.
I'll also create separate sub tasks in JIRA to record the changes required and the new features provided so each can be reviewed individually and we can have step-by-step discussions how to proceed in bringing this solution into the main trunk.

Note: as current Wicket development is getting close to the 1.3.0 release, I don't expect all of this to be merged into the trunk until after the 1.3.0 release.
But some of my proposed changes really are very light and non-intrusive, so I can imagine (and hope) those can be integrated in the trunk even before the 1.3.0 release.
That definitely would make it easier for me to provide portlet support to my own development team using the wicket core trunk and only a few additional patches.