Make *all* properties of KSPParticleEmitter cfg-configurable

[eggrobin]

For now we've just told the users "don't use damping on smoke" etc., but users don't make new mu files, they reuse the HotRockets stuff, which predates many of the niftier features.
We want users who reuse HotRockets mu files to be able to comply with our advice, so at least the following must be configurable (really killable, but we may as well be flexible).

damping (should not be used for smoke, use physical and drag instead)
rndForce, rndVelocity, rndAngularVelocity (should die)
useWorldSpace (should always be used for smoke and slow flames)

This should be fairly easy, we already do it for colorAnimation and sizeGrow.
@sarbian, I can't assign this to myself, please do so, I'll try to do it over the week-end.

[sarbian]

You need to make sure the .mu value is used if the value is not in the cfg.

[eggrobin]

Absolutely, we don't want to break all of HotRockets :-p

[eggrobin]

TODO(@eggrobin): the following should also be optionally cfg-configurable (with fallback to .mu as currently implemented).

// to be configured from a single emissionSpread curve (uniform distribution)
minEmission, maxEmission
// to be configured from a single energySpread curve (uniform distribution)
minEnergy, maxEnergy
// to be configured from a single sizeSpread curve (uniform distribution)
minSize, maxSize

Also, erratum, force is already cfg-configurable.