veyron2/ipc: 3 of n. 'Invoker and Signature' rationalisation.

- implement the changed ipc.Serve signature
- transition all code to use it and ipc.ServeDispatcher
- get rid of the ugliness around calling Serve multiple
  times to publish under multiple names in the mount table
  and instead provide AddName/RemoveName methods.

Change-Id: Ic5edd709d28e2670369986a5b0fce4cd22e3cafd
diff --git a/tools/application/impl_test.go b/tools/application/impl_test.go
index c55a5e9..bd323c9 100644
--- a/tools/application/impl_test.go
+++ b/tools/application/impl_test.go
@@ -85,7 +85,7 @@
 		t.Errorf("Listen failed: %v", err)
 		return nil, nil, err
 	}
-	if err := server.Serve("", dispatcher); err != nil {
+	if err := server.ServeDispatcher("", dispatcher); err != nil {
 		t.Errorf("Serve failed: %v", err)
 		return nil, nil, err
 	}