Remove warhammer

[Goosius1]

Backround:

• The warhammer is a lot of code for a powered-up axe with knockback, doesn't come with a propor graphic, and interferes with making stone axes.
• It just doesn't seen worth it at this point, unlike the spear, which although the native graphic in Janky, has a unique anti-cavalry role in combat
• Therefore this PR removes the warhammer

Closes #83