Resolve "Check if item-controlling can be modeled using ECA rules"

Closes #17 (closed)

eraser-base/src/main/jastadd/AdditionalTypes.jadd

 aspect AdditionalTypes {
-  public class StringList extends beaver.Symbol implements Iterable<String> {
-    private java.util.Deque<String> delegatee = new java.util.ArrayDeque<>();
+  public class ReversedList<T> extends beaver.Symbol implements Iterable<T> {
+    private java.util.Deque<T> delegatee = new java.util.ArrayDeque<>();
 
-    public java.util.Iterator<String> iterator() {
+    public java.util.Iterator<T> iterator() {
       return delegatee.descendingIterator();
     }
 
-    public void add(String s) {
-      delegatee.add(s);
+    public void add(T t) {
+      delegatee.add(t);
     }
   }
 
+  public class StringList extends ReversedList<String> {}
+  public class ItemList extends ReversedList<Item> {}
+
   public class TypedKeyMap<T> extends beaver.Symbol implements Iterable<AbstractMap.SimpleEntry<T, String>> {
     private java.util.Deque<AbstractMap.SimpleEntry<T, String>> delegatee = new java.util.ArrayDeque<>();