!u NEEDS TESTING - added a few new features in this build: Added a method of grouping nodes via a new attr, mClassGrp. The intention is that we can mark given classes as system roots and by-pass th inheritance maps. I need this for MetaRig as MetaSubSystem is also inherited from MetaRig yet I do NOT want it returned in some case.

getMetaNodes has a new flag mClassGrps to accommodate this new data

Also added FacialCore handling to MetaRig.getChidren