OSX: Improve app startup time

Importing everything (*) from AppKit takes a while, since we got 3 scripts
doing that, startup could take up to few seconds. This change makes script
import only what they need, improving startup time to fraction of second.

src/ui-macos/main.py

 import sys
 import os
 import pty
-from AppKit import *
+from AppKit import (
+  objc,
+  NSApp,
+  NSApplicationMain,
+  NSAttributedString,
+  NSFileHandle,
+  NSFileHandleDataAvailableNotification,
+  NSImage,
+  NSMenu,
+  NSMenuItem,
+  NSNotificationCenter,
+  NSObject,
+  NSStatusBar,
+  NSVariableStatusItemLength,
+)
 import my
 import models
 import askpass

src/ui-macos/models.py

-from AppKit import *
+from AppKit import (objc, NSObject)
 import my
 
 

src/ui-macos/my.py

 import os
-from AppKit import *
+from AppKit import (
+  NSBundle,
+  NSData,
+  NSDictionary,
+  NSImage,
+  NSUserDefaults,
+)
 import PyObjCTools.AppHelper