Replace GasLedger with Gas enum class

ethereumj-core/src/main/java/org/ethereum/core/Block.java

@@ -9,6 +9,8 @@ import org.ethereum.util.RLPElement;
 import org.ethereum.util.RLPList;
 import org.spongycastle.util.BigIntegers;
 
+import edu.emory.mathcs.backport.java.util.Arrays;
+
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.List;

ethereumj-core/src/main/java/org/ethereum/vm/Gas.java

@@ -0,0 +1,33 @@
+package org.ethereum.vm;
+
+/**
+ * The fundamental network cost unit. Paid for exclusively by Ether, which is converted 
+ * freely to and from Gas as required. Gas does not exist outside of the internal Ethereum 
+ * computation engine; its price is set by the Transaction and miners are free to 
+ * ignore Transactions whose Gas price is too low.
+ */
+public enum Gas {
+
+	G_STEP(1),
+	G_STOP(0),
+	G_SUICIDE(0),
+	G_SLOAD(20),
+	G_SHA3(20),
+	G_SSTORE(100),
+	G_BALANCE(20),
+	G_CREATE(100),
+	G_CALL(20),					 
+	G_MEMORY(1),
+	G_TXDATA(5),
+	G_TRANSACTION(500);
+			 
+	private int cost;
+	
+	private Gas(int value) {
+		this.cost = value;
+	}
+	
+	public int cost() {
+		return cost;
+	}
+}