Semantic lubrication.

Now instead of this on the server:

        @SuppressWarnings("unchecked")
        Address<BoardObject> addr = (Address<BoardObject>)obj.getAddress();
        return RFuture.success(addr);

Just this:

        return RFuture.success(obj.getAddress(BoardObject.class));

LMK if there is already some better to do this. NexusObject doesn't have the leaf type generic
parameter like some other libraries do.