Move q to parentclass, add SmoothedCoreSkin class
Move q to parentclass, add SmoothedCoreSkin class

The calculation of q can be moved to parent class as it should be the
same for all classes.
SmothedCoreSkin class generates splines for a smoothed core and skin
current profile, based on Alan Blasser's smoothing spline.

jensv/fluxtubestability,jensv/fluxtubestability