Adopt Output panel to use views

[sandy081]

Adopt Output panel to use views

[sandy081]

@sbatten Needed more API in IViewsService for moving output panel to output view and added them. Most importantly these new APIs replaces the usage of panel service. It has to be make sure while adopting other panels or side bar views that they should not be using panel or viewlet service and to be replaced by IViewsService. Here are the new APIs added to IViewsService:

readonly onDidChangeViewVisibility: Event<{ id: string, visible: boolean }>;
isViewVisible(id: string): boolean;

closeView(id: string): void;

Also moved registering viewlets and panels from View Containers into ViewsService. So this makes it a service that talks to viewlets and panels. Hence we shall replace all usages of panels service and viewlet service in views and panels to use IViewsService.