Enhancing portlet session management

[Eric Dalquist]

I've created https://issues.apache.org/jira/browse/PLUTO-503 and
https://issues.apache.org/jira/browse/PLUTO-504 which relate to a
portal's ability to extend the Pluto provided PortletSessionImpl.

503 simply makes some private method protected to allow a subclass to
change how portlet session attributes are namespaced.

504 adds a method to the PortletEnvironmentService for creating
PortletSession objects and modifies the PortletRequestImpl to use this
new API for creating a PortletSession if it needs one.

Neither patch will change exiting behavior, just provide an additional
hook for portals using Pluto.



I'll be applying this to trunk, 2.0-refactoring and 1.1.x later this
week unless anyone has objections.

-Eric