add READ_EXTERNAL_STORAGE permission

This is required to import certificates starting with API level 19 (KitKat 4.4)

AndroidManifest.xml

@@ -21,6 +21,7 @@
     <uses-permission android:name="android.permission.BROADCAST_STICKY" />
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
     <uses-permission android:name="android.permission.RECORD_AUDIO" />
     <uses-permission android:name="android.permission.VIBRATE"/>