This interface is implemented by an object that can provide a
Reference to itself.
A Reference represents a way of recording address information about
objects which themselves are not directly bound to the naming system.
Such objects can implement the Referenceable interface as a way
for programs that use that object to determine what its Reference is.
For example, when binding a object, if an object implements the
Referenceable interface, getReference() can be invoked on the object to
get its Reference to use for binding.