Whitespace management extension

I have been working on an extension for whitespace management, similar to what's described here: http://wiki.apache.org/xmlgraphics-fop/WhitespaceManagement

The logic of the extension is very simple: the user defines a set of alternatives that he wishes to insert at the end of a page, then if there is enough space left, FOP will pick the alternative that best matches the user's selection criteria (first fit, smallest fit, biggest fit).

This is my first work on FOP and it took me almost 2 months to reach this stage in development. But it's not the end of course, so I'm relying on your feedback to improve it.

Thank you