TerraFirmaThings

Fixes the critical issue of allowing Pigvils to despawn.

Also some new content!

Hiking Boots: Allows you to walk through tall grass and plants without a slowdown effect.

New sling ammo types:

-Require a reinforced sling to fire

-Heavy sling ammo: Does extra damage

-High-velocity sling ammo: Flies faster and farther

-Scatter sling ammo: Fires 5 projectiles in a spread

-Sparking sling ammo: Sets the target on fire