implement docking/portable switch software

The software will start on boot and will

1. detect if current hardware can be docked/portable (gpi2, piboy or rg353x), if not just exit
2. detect current mode
3. if a switch has occurred (portable to docked or docked to portable), then do this:
   • change theme as requested (go2/next) if theme was not customized (see piboy docking software)
   • change audio sink output
   • force external or internal display off
   • disable internal joystick if docked (i.e for gpi2: echo "1-1.3:1.0" > /sys/bus/usb/drivers/xpad/unbind)

For each hardware, some functions helper must exist:

• get current docking status (from gpio, kernel flag, drm)
• disable internal screen
• disable external video connector
• set internal audio speaker
• set external audio output