added helper for calculating knockback position
Merge branch 'develop' into knockback
add new weapon superclasses
add attack for melee weapons, start add knockback
Merge branch 'knockback' into melee-weapon
start add knockback logic
cleanup death logic
add knockback to melee attacks
arm less "stupid" enemies with melee weapons
reset knock back effects on player when round ends
cancel knockback effects on terrain collision
make sure undefined is not added to enemy damage statistics
increase knockback speed and improve knockback movement
Merge branch 'develop' into melee-weapon

Conflicts:
	src/js/entities/entity.js
	src/js/states/game.js
readability