ENH: boundBox 'reduce' method (related to #196)

reduce()
- parallel reduction of min/max values.
  Reduces coding for the callers.

  Eg,
      bb.reduce();

  instead of the previous method:
      reduce(bb.min(), minOp<point>());
      reduce(bb.max(), maxOp<point>());

STYLE:

- use initializer list for creating static content
- use point::min/point::max when defining standard boxes

applications/utilities/mesh/manipulation/checkMesh/checkTopology.C

@@ -569,8 +569,7 @@ Foam::label Foam::checkTopology
                             bb.min() = min(bb.min(), pts[mp[i]]);
                             bb.max() = max(bb.max(), pts[mp[i]]);
                         }
-                        reduce(bb.min(), minOp<vector>());
-                        reduce(bb.max(), maxOp<vector>());
+                        bb.reduce();
                         Info<< ' ' << bb;
                     }
                 }