model.flight: add QNH column
lib.xcsoar.analysis: store QNH from xcsoar analysis

Let the analysis take some more fixes before takeoff and after landing
to calculate the QNH based on the altitude difference between the recorderd
pressure altitude and the terrain height on ground.
setup.py: update xcsoar module version to 0.3

This one adds QNH processing
lib.xcsoar.flightpath: set QNH if provided
lib.xcsoar.flightpath: rename altitude to gps_altitude in FlightPathFix
views.upload: use baro altitude for barogram
views.track: fix forgotten FlightPathFix field name change