Add sign-in and token retrieval to Blimp

blimp/client/android/AndroidManifest.xml.jinja2

 <?xml version="1.0" encoding="utf-8"?>
 
 <!-- Copyright 2015 The Chromium Authors. All rights reserved.
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
         package="{{manifest_package}}">
     <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="21" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
     <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.GET_ACCOUNTS"/>
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
     <application android:name="BlimpApplication"
             android:label="Blimp">
         <activity android:name="BlimpRendererActivity"
                   android:launchMode="standard"
                   android:theme="@android:style/Theme.Holo.Light.NoActionBar"
                   android:configChanges="orientation|keyboardHidden|keyboard|screenSize"
                   android:hardwareAccelerated="true">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+
+        <meta-data android:name="com.google.android.gms.version"
+                android:value="@integer/google_play_services_version" />
     </application>
 </manifest>