Introduces Android API level linting, fixes all current API lint errors.

webrtc/examples/androidapp/AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           package="org.appspot.apprtc"
           android:versionCode="1"
           android:versionName="1.0">
 
     <uses-feature android:name="android.hardware.camera" />
     <uses-feature android:name="android.hardware.camera.autofocus" />
     <uses-feature android:glEsVersion="0x00020000" android:required="true" />
-    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="21" />
+    <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="21" />
 
     <uses-permission android:name="android.permission.CAMERA" />
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
     <uses-permission android:name="android.permission.RECORD_AUDIO" />
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 
     <application android:label="@string/app_name"
                  android:icon="@drawable/ic_launcher"
@@ skipping 20 matching lines @@
         </activity>
 
         <activity android:name="CallActivity"
                   android:label="@string/app_name"
                   android:screenOrientation="fullUser"
                   android:configChanges="orientation|screenSize"
                   android:theme="@style/CallActivityTheme">
         </activity>
     </application>
 </manifest>