Minor fixes to MAVLink
Merge pull request #1026 from PX4/mavlink_fixes

Minor fixes to MAVLink
ubx driver: fix unit of speed and position accuracy estimate
Merge pull request #1029 from PX4/ubxaccuracyunit

ubx driver: fix unit of speed and position accuracy estimate
ubx: disable all debug messages
ubx: send update only if got POSLLH & VELNED & TIMEUTC
Merge branch 'ubx_no_debug' into inav_gps_delay