AI Air Force v1.1

This is my attempt to make the AI use air units.

Change Log
AI Air Force Updates Change Log

Version 1.1
-- Changes effect all air units (player and AI)
-- All AI now prefer to research FLIGHT and ADVANCED FLIGHT
-- Air units no longer require Aerodrome (but can still use it). Now require a City Center only.
-- City center can now hold two air units.
-- Air units no longer require resources to be built.
-- Air units cost 50% of their normal cost
-- New air stats to accommodate their cheaper build costs
-- BIPLANE: Range increased to 4; RangedCombat str reduced to 40; No Strategic resource needed (None in Vanilla)
-- FIGHTER: Range increased to 5; RangedCombat str reduced to 50; No Strategic resource needed
-- P51: Range increased to 6; RangedCombat str reduced to 50; No Strategic resource needed (None in Vanilla)
-- JET FIGHTER: Range increased to 7; RangedCombat str reduced to 65; Base sight range increased to 5; No Strategic resource needed
-- BOMBER: No Strategic resource needed
-- JET BOMBER: Base sight range increased to 5; No Strategic resource needed

-- NOTE: For Jet Bomber and Jet Fighter, vanilla has their base sight range at 2 (earlier air units are set to 4)

AI Biplane intercepting my Jet Fighter