Function legacy_skill_set 

pub fn legacy_skill_set(faction: &FactionEntry, navy: bool) -> String

Returns the skill set of a faction’s armies or navies (MILITARY_FORCE_LEGACY/CAMPAIGN_SKILLS #1).

The key replaces sub_cult_ in the subculture key with army_legacy_ or navy_legacy_ (att_sub_cult_roman_west gives att_army_legacy_roman_west).