Custom Warheads refactor

Changes included:

Warhead code split out of weapon code and refactored.
Warhead functionality now split into several classes, each handling one effect/impact.

Additional custom warheads can now be defined and called via yaml.
Custom warheads inherit the abstract class Warhead,
which provides target check functions.

Custom warheads have to define their own impact functions,
and can also define their own replacement for check
functions.

mods/ra/maps/drop-zone-w/map.yaml

@@ -313,20 +313,22 @@ Weapons:
 			Inaccuracy: 3c341
 			Image: 120MM
 			ContrailLength: 30
-		Warhead:
+		Warhead: SpreadDamage
 			Spread: 128
 			Versus:
 				None: 60%
 				Wood: 75%
 				Light: 60%
 				Heavy: 25%
+			InfDeath: 2
+			Damage: 250
+		Warhead@1Eff: CreateEffect
 			Explosion: large_explosion
 			WaterExplosion: large_splash
-			InfDeath: 2
-			SmudgeType: Crater
-			Damage: 250
 			ImpactSound: kaboom12.aud
 			WaterImpactSound: splash9.aud
+		Warhead@2Smu: LeaveSmudge
+			SmudgeType: Crater
 	SubMissile:
 		ROF: 250
 		Range: 32c0
@@ -340,19 +342,21 @@ Weapons:
 			Image: MISSILE
 			Trail: smokey
 			ContrailLength: 30
-		Warhead:
+		Warhead: SpreadDamage
 			Spread: 426
 			Versus:
 				None: 40%
 				Light: 30%
 				Heavy: 30%
+			InfDeath: blownaway
+			Damage: 400
+		Warhead@1Eff: CreateEffect
 			Explosion: large_explosion
 			WaterExplosion: large_splash
-			InfDeath: blownaway
-			SmudgeType: Crater
-			Damage: 400
 			ImpactSound: kaboom12.aud
 			WaterImpactSound: splash9.aud
+		Warhead@2Smu: LeaveSmudge
+			SmudgeType: Crater
 
 Voices: