Added 4 cards from AHK

* Added Cartouche of Strength
* Added Nest of Scarabs (More correct implementation than existing one)
* Added Soul-Scar Mage
* Added Battlefield Scavenger

Mage/src/main/java/mage/abilities/dynamicvalue/common/EffectKeyValue.java

@@ -0,0 +1,45 @@
+package mage.abilities.dynamicvalue.common;
+
+
+import mage.abilities.Ability;
+import mage.abilities.dynamicvalue.DynamicValue;
+import mage.abilities.effects.Effect;
+import mage.game.Game;
+
+/**
+ * @author stravant
+ */
+public class EffectKeyValue implements DynamicValue {
+    private String key;
+    private String description;
+
+    public EffectKeyValue(String key) {
+        this.key = key;
+        this.description = key;
+    }
+
+    public EffectKeyValue(String key, String description) {
+        this(key);
+        this.description = description;
+    }
+
+    @Override
+    public int calculate(Game game, Ability source, Effect effect) {
+        return (Integer)effect.getValue(key);
+    }
+
+    @Override
+    public EffectKeyValue copy(){
+        return new EffectKeyValue(this.key, this.description);
+    }
+
+    @Override
+    public String toString() {
+        return "equal to";
+    }
+
+    @Override
+    public String getMessage() {
+        return description;
+    }
+}