NodeTypingsInstaller.handleMessage should treat PackageInstalledResponse roughly the same as SetTypings

[amcasey]

In particular, PackageInstalledResponse should probably be a ProjectResponse and handleMessage should call

                    this.projectService.updateTypingsForProject(response);

                    if (this.socket) {
                        this.sendEvent(0, "setTypings", response);
                    }

I'll leave it to the implementer to decide whether the event name should be different - VS doesn't need to distinguish.