Fix broken test in MvcNamespaceTests

The testDefaultConfig() method in MvcNamespaceTests creates a new Date()
in its test fixture but then performs an assertion against a hard coded
data string of "2013-10-21". This test therefore only passed yesterday,
on October 21, 2013.

This commit addresses this by changing the hard coded date string to one
based on the current date.

Issue: SPR-10665, SPR-8826
Add support for WebSocket Protocol Extensions

This commits adds simple, overridable WebSocket Extension
filtering during the handshake phase and adds that
information in the WebSocket session.

The actual WebSocket Extension negotiation happens
within the server implementation (Glassfish, Jetty, Tomcat...),
so one can only remove requested extensions form
the list provided by the WebSocket client.

See RFC6455 Section 9.

Issue: SPR-10843