No Barbarian XP Cap

Removes the soft cap on combat with Barbarians after gaining one promotion. The soft cap is the limit after gaining 1 promotion that restricts XP gains from combat with barbarians to 1 XP point per combat. NOTE: This mod doesn't entirely work as intended. It makes barbarians give more xp than they should based on the opposing units xp modifer (barracks, armory, etc) I may get round to fixing that at some point, but I'm leaving it like that for now. So be aware, it's a little broken. The AI gains the same benefit as the player, though.