This class is a ThreadLocal class that contains the servlet information. In addition,
it supports a Map that allows other aspects of the framework to create place
their own context objects into the thread local context.
This method will lookup a named object and return it. The object is
looked up by name. If the object doesn't exist, the activator object is
called to create a new instance of the object before it is returned.
Parameters: name - The name of the object to return Parameters: activator - An PageFlowContextActivator that will create the new object ifit doesn't exist. The object stored by the name.