Added utility function to get ITK shape label map
Added utility function to get ITK shape label map

This function is useful any time shape attributes from labeled objects
are needed.

cjh1/tomviz,mathturtle/tomviz,OpenChemistry/tomviz,mathturtle/tomviz,cjh1/tomviz,mathturtle/tomviz,OpenChemistry/tomviz,thewtex/tomviz,OpenChemistry/tomviz,cryos/tomviz,OpenChemistry/tomviz,cjh1/tomviz,thewtex/tomviz,cryos/tomviz,thewtex/tomviz,cryos/tomviz