RTK moving base supported

#### Issue details
Hi all, I'm playing with RTK (hardware HERO+).
With the new firmware 1.40 of UBLOX NEO-MP8, the moving base is supported, which allows the base of the differential GPS to move. In mission planner I see a tick for "moving base" under the RTK/GPS inject tab, but when I click it, change window and come back, the tick is gone. I was wondering if that feature is currently supported and if using the tick, it enables all the UBX messages accordingly to support the moving base.

#### Platform
[ ] All
[ ] AntennaTracker
[ x ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

Start in Mission Planner's RTK/GPS inject settings, focusing on the "moving base" checkbox and how its value is saved when the window is reopened. Review the UBLOX NEO-MP8 moving-base support described in the issue and determine the expected UBX configuration. Done means the setting's support status is clear and, if supported, the checkbox persists and configures the required messages.

Written by the indexing model from the issue text.