Fixing bugs found when implementing Bidirectional Iterator unit tests.

-Fixed: AbstractList/ImmutableList/ArraySet/ArrayMap skip/back implementation was causing crashes and didn't update the last returned value.
-Fixed: ArraySet/ArrayMap previous was not subtracting before returning value.
-Fixed: BidirectionalIterator back was calling the object variant instead of the TypeSpecific Variant.
-Fixed: TreeSets/Maps Iterator now fully supports backwards Iterating.
-Added: Specialized skip/back function to improve speed in ImmutableHashSet/LinkedHashSet/CustomLinkedHashSet

src/builder/resources/speiger/assets/collections/templates/sets/ArraySet.template

@@ -924,8 +924,8 @@ public class ARRAY_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE im
 		@Override
 		public KEY_TYPE PREVIOUS() {
 			if(!hasPrevious()) throw new NoSuchElementException();
-			lastReturned = index;
-			return data[index--];
+			--index;
+			return data[(lastReturned = index)];
 		}
 		
 		@Override
@@ -964,8 +964,9 @@ public class ARRAY_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE im
 		@Override
 		public int skip(int amount) {
 			if(amount < 0) throw new IllegalStateException("Negative Numbers are not allowed");
-			int steps = Math.min(amount, (size() - 1) - index);
+			int steps = Math.min(amount, size() - index);
 			index += steps;
+			if(steps > 0) lastReturned = Math.min(index-1, size()-1);
 			return steps;
 		}
 		
@@ -974,6 +975,7 @@ public class ARRAY_SET KEY_GENERIC_TYPE extends ABSTRACT_SET KEY_GENERIC_TYPE im
 			if(amount < 0) throw new IllegalStateException("Negative Numbers are not allowed");
 			int steps = Math.min(amount, index);
 			index -= steps;
+			if(steps > 0) lastReturned = Math.min(index, size()-1);
 			return steps;
 		}
 	}