GPS: initial import of gps config code

This is imported from ublox.c:
http://autoquad.googlecode.com/svn/trunk r321
GPS: remove some unused code
GPS: more cleanup
GPS: convert the AutoQuad calls to PiOS

Switch to using PIOS_COM_SendChar etc where appropriate.
Still need to cleanly configure the GPS port.
GPS: connect configuration code to GPS module
GPS: document the UBX packets a bit better

Also a method that will send a packet plus a
checksum that isn't used yet.
GPS: refactor to use checksum message to send packets

Now the methods just prepare the data, the send method
takes care of sending the preamble, checksum, and such.
GPS: set baud rate to 57600
GPS: fix typo
GPS: improve baud configuration

Now it has preprogrammed strings for all the
GPS port speed options. They are preprogrammed
to avoid calculating the checksum onboard.
GPS: configure for correct baud rate
Freedom: enable sending on GPS port
Sparky: enable sending on GPS port
Quanton: enable sending on GPS port
FlyingF3: enable sending on GPS port
FlyingF4: enable sending on GPS port
Revolution: enable sending on GPS port
RevoMini: enable sending on GPS port
GPS: need to include NAV-STATUS message
GPS: display if a differential fix is acquired