Update passphrase caching notification strategy.

On platforms (API >= 11) that support receiving click events within
a notification, we change the notification format so that users
can "lock" TextSecure with a click.

For all platforms, we change the notification icon in the status
bar from a "lock" to an "unlock," to better reflect the situation.

This is all part of the master plan for eliminating the passphrase
timeout option.

res/drawable/notify_panel_notification_icon_bg_tile.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2011 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+  
+          http://www.apache.org/licenses/LICENSE-2.0
+  
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<bitmap
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:tileMode="repeat"
+    android:src="@drawable/notify_panel_notification_icon_bg"
+    />