GPS on board configuration

This PR adds a few GPS related features when using UBX mode:
- automatically attempt to configure the GPS to the correct baud rate (it tries this at a couple of baudrates)
- configure the GPS to output the messages we use at the appropriate rate
- detect the GPS version and store that in UBloxInfo field


This is inspired and based on http://autoquad.googlecode.com/svn/trunk/onboard/ublox.c . I left his copyright header in the ubx_cfg.c file as well.