First step in the attack mechanism's refactor.

Enabled firing multiple armaments at a target simultaneously.
Each armament defines own cursor for targeting.
The force attack modifier influences armament choice for target.
Autotargeting modified to handle firing multiple armaments simultaneously.
As a consequence, healers (medics) no longer require separate Heal
activity and AttackMedic and AutoHeal traits.

OpenRA.Mods.Common/Warheads/DamageWarhead.cs

@@ -27,6 +27,14 @@ namespace OpenRA.Mods.Common.Warheads
 		[Desc("Damage percentage versus each armortype.")]
 		public readonly Dictionary<string, int> Versus;
 
+		public override bool IsValidAgainst(Actor victim, Actor firedBy)
+		{
+			if (Damage < 0 && victim.GetDamageState() == DamageState.Undamaged)
+				return false;
+
+			return base.IsValidAgainst(victim, firedBy);
+		}
+
 		public static object LoadVersus(MiniYaml yaml)
 		{
 			var nd = yaml.ToDictionary();

OpenRA.Mods.Common/Warheads/Warhead.cs

@@ -42,7 +42,7 @@ namespace OpenRA.Mods.Common.Warheads
 		public abstract void DoImpact(Target target, Actor firedBy, IEnumerable<int> damageModifiers);
 
 		/// <summary>Checks if the warhead is valid against (can do something to) the actor.</summary>
-		public bool IsValidAgainst(Actor victim, Actor firedBy)
+		public virtual bool IsValidAgainst(Actor victim, Actor firedBy)
 		{
 			if (!AffectsParent && victim == firedBy)
 				return false;