ModuleLandingGear fixes for 0.25

Since in 0.25 physics significance = 1 is not hardcoded in the PartModule any longer, its possible to have stock-module landing gear with actual drag and such.

Quick slap-fix, set drag to 0 and the partmodule's drag overrides to 0 too.
Merge pull request #15 from Taverius/master

ModuleLandingGear fixes for 0.25 LGTM