attack ground unit task, melee icon
	modified:   LibreSTR/CMakeLists.txt
	modified:   LibreSTR/GameObject.cpp
	modified:   LibreSTR/GameObject.h
	modified:   LibreSTR/GameState.cpp
	new file:   LibreSTR/units/AttackGroundUnitTask.cpp
	new file:   LibreSTR/units/AttackGroundUnitTask.h
	modified:   LibreSTR/units/GroundUnit.cpp
	modified:   LibreSTR/units/GroundUnit.h
	modified:   LibreSTR/units/GroundUnitIdentity.cpp
	modified:   LibreSTR/units/GroundUnitIdentity.h
	modified:   LibreSTR/units/MGroundUnit.cpp
	modified:   LibreSTR/units/MGroundUnit.h
	modified:   assets/melee.res
	new file:   assets/melee_icon.png
	new file:   assets/melee_radial_icon.png
	new file:   assets/melee_radial_icon_hover.png