Change how shock damage is calculated

After a fair amount of hair pulling, seeing how Dreammaker is unable to
use any function more complex than square roots and powers, I've used
the following formula

Damage = round(power^(1/3)*(rand(15,20)/10))

Changelog was also fixed and the snowflake exception for the power glove
was removed. If the grid contains dozens of DeLoreans, your target is
going to get it big time