methods for placing session data in a remote store for load balancing

[mortonda@…]

To facilitate load balancing, we need to have some methods to put the session store for php into sql or memcached. Ideally, this should be modular so that it can be switched out easily.

If it's not too much trouble, this could make 1.0.3, but it may have to wait for 1.0.4 or 1.1.0