CORE-4360 Updates to allow multi app deletes.

Updated AppUserServiceFacade::deleteAppFromWorkspace to accept a list of App IDs, required by the updated service endpoint.
Updated AppsViewPresenter::onDeleteClicked to pass all selected App IDs to the deleteAppFromWorkspace service call, and to remove all selected apps from the view on success.
Added AppsViewPresenter::getAllSelectedApps method.