[Android] USB

1. Docs
   
   • USB Host and Accessory
     http://developer.android.com/guide/topics/usb/index.html
   • USB Accessory
     http://developer.android.com/guide/topics/usb/accessory.html
   • USB Host
     http://developer.android.com/guide/topics/usb/host.html
   • Android Open Accessory Development Kit
     http://developer.android.com/guide/topics/usb/adk.html
     
2. xxx