Removed the non-existent system variable SPELLFAILURE from the docs and updated the nav lists from "Pre-Defined" Variables to "System" Variables
Issue#: DOCS-309


git-svn-id: svn+ssh://svn.code.sf.net/p/pcgen/code/Trunk@24726 ef53c05b-3124-4d59-ae7d-fe3273f42be7