Vehicle dismounting and movement animations.

Dismounting is now done using the same key as mounting to eliminate confusion. Dismounting near a door will not go through the door so you do not accidentally leave the level.

Movement animations for vehicles are dependent on player movement velocity.
Fix blimp and golfcart offset. Removed insructions
Merge pull request #2172 from niamu/vehicles

Vehicle cleanup
Fix broken test_give_taco_meat
Merge pull request #2184 from niamu/test_taco_meat

Fix broken test_give_taco_meat