More "SetExternalMultiplier"

While modding, it is nearly impossible to mod things like absorption, damagemultiplier, hungerrate and stuff like this, cause the game itself, or other mods will undo or totally screw it up.

This is because you only added "SetRate" or "SetAbsorption" or even not a fucntion just damagemultiplier = x...
Instead we really need more like "SetExternalSpeedMultiplier".  This is what we also need for all the other stuff, to safely add boosts and remove them again, without screwing up other mods/game mechanics.