To specify TOC properties in plugin.xml:
; TocFilename = name for contents file, always toc.xml for primary
; TocPrimary = Yes (default, toc.xml) or No (secondary)
; TocExtradir = path to dir for additional docs to include
; in search index, even if not referenced from any toc topic
See §12.4.4 Configuring contents properties for Eclipse Help.