build tool to regenerate component update sites from published JBT aggregate

When we released JBT 4.1.0.Final, we didn't publish the individual projects as sites themselves, so now when we're trying to aggregate JBT 4.1.1.Alpha2 using a combination of unchanged older projects + changed newer projects, we're unable to do so.

We could rebuild the projects from source, but it would be better to simply re-aggregate the binaries in order to produce subset sites which match the content of the released JBT site, but only for those individual projects.

This would allow us to swap in/out projects like GWT, Freemarker, Birt, Hibernate and Portal, which haven't changed yet since JBT 4.1.0.Final was released.