Bug and stability fixes.
- Added "Raspberry Pi 3 Model B" support to image (use the integrated Wi-Fi, not an external dongle as required with older hardware).
- Upgraded Raspbian and Raspberry Pi firmware on image.
- Removed client expiry code - caused issue on units with a GPS installed that was not getting a fast GPS lock (WebUI shows messages being received, EFB does not).
- Dongle handling improvements.