This reverts commit ad783b97.

Redmine: #1931

Redmine: #1872

Redmine: #1858

Added helper class LayerFillLimits to assist in generating the correct limits for the graded layer approximation

Move slicing of multilayer to multilayer itself and provide default implementations of top/bottomZParticles in Layer and ParticleLayout

Move MultiLayer::getZLimits() to global function and override IParticle::createSlicedFormFactor in Particle

Move zDifference method to global function and use it to transform to new coordinates when particle is defined in a different layer as its containing layer

Added SlicedFormFactorList class that contains list of form factors and the layer indices corresponding to them

Ambient material is now set based on the position of the form factor instead of statically (core shell tests failing now)