introduce bitloops

src/main/java/puzzle/Export.java

@@ -75,6 +75,11 @@ public record Export() {
          for (var cell1 : cell) empty.setClue(cell1);
          return empty;
       }
+      public static Clues of(Cell... cells) {
+         var c = createEmpty();
+         for (var cell : cells) c.setClue(cell);
+         return c;
+      }
       public Clued deepCopyGrid() { return new Clued(new Clues(c.lo, c.hi, c.vlo, c.vhi, c.rlo, c.rhi, c.xlo, c.xhi)); }
       public static Clued parse(String s) {
          var c     = createEmpty();