ADD:FEAT now respects (and removes from the ability to select) MULT:YES, STACK:NO selections on a given Feat regardless of the Nature of the Feat on which it other items were selected
Includes Unit Test validating behavior

Issue#: CODE-1921, CODE-2436


git-svn-id: svn+ssh://svn.code.sf.net/p/pcgen/code/Trunk@22789 ef53c05b-3124-4d59-ae7d-fe3273f42be7