Collapses a given faction header or sub-header in the Reputation UI.
Faction headers include both major groups (Classic, Burning Crusade, Wrath of the Lich King, Inactive, etc.) and the sub-groups within them (Alliance Forces, Steamwheedle Cartel, Horde Expedition, Shattrath City, etc.).
See also Faction functions.
index- Index of an entry in the faction list; between 1 and GetNumFactions() (