UserHandle to UserSerialNo mapping

Use AtomicFile for usermanager files.

Added a MANAGE_USERS permission that apps (signature permission) can use
to create/query/modify/remove users.

Change-Id: I5cf232232d0539e7508df8ec9b216e29c2351cd9
diff --git a/packages/SystemUI/AndroidManifest.xml b/packages/SystemUI/AndroidManifest.xml
index 676bfd0..e13378f 100644
--- a/packages/SystemUI/AndroidManifest.xml
+++ b/packages/SystemUI/AndroidManifest.xml
@@ -15,7 +15,7 @@
     <uses-permission android:name="android.permission.EXPAND_STATUS_BAR" />
     <uses-permission android:name="android.permission.REMOTE_AUDIO_PLAYBACK" />
 
-    <uses-permission android:name="android.permission.MANAGE_ACCOUNTS" />
+    <uses-permission android:name="android.permission.MANAGE_USERS" />
 
     <!-- Networking and telephony -->
     <uses-permission android:name="android.permission.BLUETOOTH" />