Hybrid glider - assembling hull and propellers

[bsb808]

Working on #247. Scaling the mesh files to match the physical dimensions has a side effect of not having hybrid glider propellers in correct position on vehicle.

Suggest addressing this by modifying the glider_hybrid_whoi.xacro URDF, but running out of time.

Also suggest testing that propellers still spin when commanded as expected.

[woensug-choi]

#246 (comment)