Delete GetCivData from MapGeneratorWorker.cpp which is redundant with the ReadJSONFile from rP20129.
Unify civ file loading from gui/common/functions_civinfo.js and rmgen/library.js in globalscripts/Templates.js.
Delete the two forgotton headers in rP20507.
Refs #4868, #4804, D900.
Differential Revision: https://code.wildfiregames.com/D1062
Discussed with: leper