add preferences view

not populated yet

ZeroTier One/PreferencesViewController.swift

@@ -0,0 +1,18 @@
+//
+//  PreferencesViewController.swift
+//  ZeroTier One
+//
+//  Created by Grant Limberg on 6/23/16.
+//  Copyright © 2016 ZeroTier, Inc. All rights reserved.
+//
+
+import Cocoa
+
+class PreferencesViewController: NSViewController {
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        // Do view setup here.
+    }
+    
+}