Convert contrails to world coords.
Pass WorldRenderer to AnimationWithOffset.OffsetFunc.
Remove unnecessary PPos.FromWPosHackZ() usage.
Convert WithRotor to world coords.
Convert SmokeTrailWhenDamaged to world coords.
Convert RenderUnitSpinner -> RenderUnit + WithSpinner.

Also sets correct offsets for the units that use it.
Rewrite ThrowsParticle using world coordinates.

The old dynamics were crazy, so this implements
a simpler model using a cubic lerp.
Remove Turret and PVecFloat cruft.
Merge pull request #2917 from pchote/turret-cleanup

Remove Turret and PVecFloat cruft.