Removes falling in space

You can still be stunned, slip (unfortunately), be pushed or die, your
icon just remains upright to simulate zero gravity. Upon being dragged
into the station, your body thumps to the ground inside the airlock.
It's pretty neat.
Removes slipping in space

Added a standing check before damage is applied by lube. Aliens and
hulks won't take damage for sliding on lube.
Merge pull request #2676 from Tenebrosity/nospacefallspls

Removes falling over in space, fixes #2680