Change design of GlobalSkillCostFacet to be a "Scoped" Facet
	info is stored relative to another item, in this case Skills stored in relation to their cost
	Effectively this is leveraging an AbstractMapToSourcedListFacet, but with a different name
Includes new PCG round robin tests

Issue#: CODE-1975, CODE-1976


git-svn-id: svn+ssh://svn.code.sf.net/p/pcgen/code/Trunk/pcgen@19161 ef53c05b-3124-4d59-ae7d-fe3273f42be7