Check request param to recognize JSF 2 Ajax requests

Previously we checked the "Faces-Request" header only.
Now we try to delegate the call to
PartialViewContext.isAjaxRequest() first. If a FacesContext
is unavailble for some reason we also check the
"javax.faces.partial.ajax" request parameter.
Correct spring-binding/.classpath to use IVY_CACHE
Updates to readme, javadoc, and sample poms.

Issues: SWF-1507
Upgrade to Spring 3.1.1
Update repository information in docs
Spring Web Flow 2.3.1 release
Avoid releasing FacesContext in PropertyAccessor

Issue: SPR-1558
Skip iteration delivering PostRestoreStateEvent

Recent updates to Mojarra added a SKIP_ITERATION hint when delivering
the PostRestoreStateEvent.  Web Flow should follow the same logic.

Issue: SWF-1549
Backport-Commit: cd3d8be81972a8f9db9d5dc6bdf6148652fc6b1a
Upgrade to Spring Framework 3.2

Issue: SPR-1580
Upgrade Spring Security and switch to snapshot label

Issue: SWF-1581