public.js.flight: use addFeatures instead of drawFeatures in showPlanePosition
public.js.flight: use addFeatures instead of drawFeatures in showPlanePosition

When moving the map the plane icons where not redrawn when they where
only updated with drawFeatures.

Turbo87/skylines,Turbo87/skylines,shadowoneau/skylines,shadowoneau/skylines,dkm/skylines,skylines-project/skylines,Harry-R/skylines,Harry-R/skylines,shadowoneau/skylines,Turbo87/skylines,kerel-fs/skylines,snip/skylines,kerel-fs/skylines,RBE-Avionik/skylines,TobiasLohner/SkyLines,RBE-Avionik/skylines,kerel-fs/skylines,TobiasLohner/SkyLines,dkm/skylines,TobiasLohner/SkyLines,skylines-project/skylines,RBE-Avionik/skylines,Harry-R/skylines,Harry-R/skylines,skylines-project/skylines,RBE-Avionik/skylines,dkm/skylines,Turbo87/skylines,shadowoneau/skylines,snip/skylines,dkm/skylines,skylines-project/skylines,snip/skylines