Quick fix and new store item

Quick fix involving the rapid fire powerup messing up cooldowns for everything.

Also removed the "projectile speed" item in the upgrades menu because, it was kind of useless since, everything goes directly towards you. You can't really miss. I replaced it with a slightly expensive upgrade that improves powerups. It improves all powerup cooldowns, and enhances them.

I might later end up giving options to upgrade the powerups individually but for now this works.