code: public static <V> Cursor<V, V> slice(Object[] btree, boolean forwards)
      {
          Cursor<V, V> r = new Cursor<>();
          r.reset(btree, forwards);
          return r;
      }
docs: Returns an Iterator over the entire tree
  
  @param btree    the tree to iterate over
  @param forwards if false, the iterator will start at the end and move backwards
  @param <V>
  @return