Fixed height computation. Moved adding of gravity center
 shift, which probably fixed the problems we had with
 'wheels inside kart chassis' tests earlier.
Set the graphical suspension depending on physical suspension (capped).
Adjusted graphical chassis to be 0.1 higher to have similar look at previously
and avoid graphical chassis going into terrain,
Fixed shadows with a hack.
Removed artificial Y offset to allow evaluation of more karts.
Make the graphical y offset configurable (and basically disable
it for now by setting it to 0).
Fix suspension to some more realistic values.
Use sqrt(speed) to scale the collision impulse, which results in
weaker impulses when hitting the terrain.
Merge remote-tracking branch 'origin/master' into no_floating

Conflicts:
	src/karts/kart.cpp
Added some debug output to get more info for #1464 (unnecessary download
of addon icons). To be removed later.
Merge branch 'no_floating'