Introduction of formsets in wizards.

[pagles]

This one is not ready for pulling (docs missing, not yet rolled out in production). All tests pass plus any new functionality is tested ( I even increased coverage :) ).

I 'm sending the pull request because I would like your thoughts on the API changes. Also it only works with a cache session backend (the default session backend cannot pickle formsets).

So please if you find the time provide some feedback on the changes so I can work on them while I prepare the docs and I test it in a production environment.

Thanks, Yorgos

[supercodepoet]

I will try and get to this early next week.