Boss battle rewards, more gladiators in shop, balancing v0.937.6

Quest battles with bosses are now giving one Universal Item as reward. Rarity has some randomization, but it mainly depends on how many arenas you’ve finished. Reason being is that we felt like boss fights could use better rewards. Synergetic universal items are excluded because they might not be useful for every situation.

There are now more gladiators and items appearing in the shop as you complete more arenas.

Several universal items are buffed to be more useful. And several units are nerfed or buffed after playtesting as well as players feedback.