Core: added some comments to data.h closes inviwo/inviwo-dev#1034
Core: added some comments to data.h closes inviwo/inviwo-dev#1034


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