Wave weapon upgrade, secondary upgrades, spread weapon balance

Wave weapon upgrade!

Level 10 -> applies Cold (6s slow) to enemies hit.

Spread weapon

now only has a 25% chance to create another layer of spread shots, but also has 25% chance to crit for 3x damage.

Added secondary upgrades:

Weapon	Upgrade	Effect
Spiral		Projectile duration +50%
Staff		50% chance to crit for 3x damage
Spread		Projectile duration +50%
Wave		Projectile duration x3