Support memoization

[broneill]

Define a Memoized annotation which caches the result of a remote call on the client side. A memoized method which returns void also supports memoization.

When the remote object is disconnected, clear the cached results. If the annotation is declared as "sticky", then don't clear the cached results until the remote object is reconnected.

[broneill]

Should exceptions other than the declared remote exception be memoized too?

[broneill]

Consider adding a "proactive" option which calls the method when the remote object is transported, avoiding a remote call later.

[broneill]

I don't think the "proactive" option fits with this feature, considering that the method cannot accept parameters. Instead, define a separate Data annotation.