title: Core Data: how to reset everything when setup with loadPersistentStores?
body: <p>When using the "new" iOS 10 Core Data setup with <code>loadPersistentStores</code>, how can I reset/delete everything? I would like to avoid using the entity names but would love to use something like <code>destroyPersistentStore</code>.</p>
  
  <p>I setup my stack the following:</p>
  
  <pre><code>persistentContainer = NSPersistentContainer(name: "CoreData", managedObjectModel: mom)
  let storeDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
  let url = storeDirectory.appendingPathComponent("CoreData.sqlite")
  let description = NSPersistentStoreDescription(url: url)
  description.shouldInferMappingModelAutomatically = true
  description.shouldMigrateStoreAutomatically = true
  persistentContainer.persistentStoreDescriptions = [description]
  
  persistentContainer.loadPersistentStores(completionHandler: { (_, error) in
      guard let error = error as NSError? else { return }
      fatalError("Unresolved error: \(error), \(error.userInfo)")
  })
  persistentContainer.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
  persistentContainer.viewContext.undoManager = nil
  persistentContainer.viewContext.automaticallyMergesChangesFromParent = true
  </code></pre>
  
  <p>I only found solutions with e.g. BatchDeleteRequests where I need to know all entity names, but I would like something more generic and reset everything - I need the most performant/safest way when the user logs out.</p>