Core: minor refactoring of Interpolation class
Core: minor refactoring of Interpolation class

inviwo/inviwo,inviwo/inviwo,inviwo/inviwo,Sparkier/inviwo,Sparkier/inviwo,Sparkier/inviwo,inviwo/inviwo,Sparkier/inviwo,inviwo/inviwo,inviwo/inviwo,Sparkier/inviwo