D1761/rP22984 enabled workshops for all civilizations and removed siege engines and technologies from the fortresses, D2532/rP23746 made champion cavalry trainable at the stable. This patch:
* enables the stable for all civilizations:
* removes cavalry from all barracks;
* removes champion cavalry from all fortresses;
* deletes the now obsolete `{civ}_champion_cavalry_barracks.xml` templates;
* removes cavalry technologies from corral and fortress;
* makes champion chariots trainable at the stable;
* removes champion chariots from all fortresses;
* deletes the now obsolete `{civ}_champion_chariot_barracks.xml` templates;
* unlock champions technology 30% cheaper;
* tweaked cavalry technology costs;
* the first cavalry speed technology is made available in the village phase;
* the second cavalry speed technology is replaced with one that instead reduces cavalry training by 10%, available in town phase;
* the Nisean horses technology only affects cavalry spearmen, available in city phase;