HPCC-11660 DOCS:Add System Admin guide to Doc. Set

Fix HPCC-11660 DOCS:Add System Admin guide to Doc. Set
Add System Admin Doc to HPCC document set
Also adding the structures to enable
automate building.

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>

@JamesDeFabia please review.
This filename is unlike all the other books
DOCBOOK_TO_PDF( ${FO_XSL} HPCCSystemAdministratorsGuide.xml "HPCCSystemAdministratorsGuide" "SA-Mods")