added subtraction logic to enough()

+ added subornation logic to enough(). We do not want to mix the public
subtract() call with this method. As doing so would mean that either a)
subtraction can go below 0 (this should not happen) or b) we break this
function with exceptions. This is a work around for these scenarios.

Mage.Tests/src/test/java/org/mage/test/mana/ManaTest.java

@@ -1,6 +1,5 @@
 package org.mage.test.mana;
 
-import junit.framework.Assert;
 import mage.Mana;
 import mage.constants.ColoredManaSymbol;
 import mage.constants.ManaType;

Mage/src/mage/Mana.java

@@ -507,7 +507,13 @@ public class Mana implements Comparable<Mana>, Serializable, Copyable<Mana> {
      */
     public boolean enough(final Mana avail) {
         Mana compare = avail.copy();
-        compare.subtract(this);
+        red -= avail.red;
+        green -= avail.green;
+        blue -= avail.blue;
+        white -= avail.white;
+        black -= avail.black;
+        colorless -= avail.colorless;
+        any -= avail.any;
         if (compare.getRed() < 0) {
             compare.setAny(compare.getAny() + compare.getRed());
             if (compare.getAny() < 0) {