Add a soul multiplier for higher diffuctlies in new explore

with the new explore re-work came a larger gold multiplier up to 7.6x but to still get more souls you would still have to go to the older difficulty mode which seemingly defeats the purpose of the new difficulty levels and with the addition of medals and needing at least 60000 souls to max out one troop the game just becomes one long grind just to have the chance of upgrading to the next level, since the medal system is a pass/fail which means if you need 30k souls to give the final medal and it fails that could be 30k souls down the drain that could have been used to upgrade troops