Upgrade Fixes (Early Access 32.0)

[list] [*] Objects under the floor will now render under the floor [*] Reworked ammo upgrades to work immediately [*] Stopwatch is stronger and stacks [*] Bullet collision size now accurately reflects visual size, bullet sprites can be scaled up for even bigger bullets [*] Discounts now stack multiplicatively [*] Mech Fist and Wavy Snake now function properly and also stack [/list]