ENH: boundBox improvements (#2609)

- construct boundBox from Pair<point> of min/max limits,
  make sortable

- additional bounding box intersections (linePointRef), add noexcept

- templated access for boundBox hex-corners
  (used to avoid temporary point field).
  Eg, unrolled plane/bound-box intersection with early exit

- bounding box grow() to expand box by absolute amounts
  Eg,

      bb.grow(ROOTVSMALL);   // Or: bb.grow(point::uniform(ROOTVSMALL));
  vs
      bb.min() -= point::uniform(ROOTVSMALL);
      bb.max() += point::uniform(ROOTVSMALL);

- treeBoundBox bounding box extend with two or three parameters.
  The three parameter version includes grow(...) for reduced writing.
  Eg,

      bb = bb.extend(rndGen, 1e-4, ROOTVSMALL);

  vs
      bb = bb.extend(rndGen, 1e-4);
      bb.min() -= point::uniform(ROOTVSMALL);
      bb.max() += point::uniform(ROOTVSMALL);

  This also permits use as const variables or parameter passing.
  Eg,

      const treeBoundBox bb
      (
          treeBoundBox(some_points).extend(rndGen, 1e-4, ROOTVSMALL)
      );

applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformationSurfaces/conformationSurfaces.C

@@ -605,7 +605,7 @@ Foam::conformationSurfaces::conformationSurfaces
 
 // * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //
 
-bool Foam::conformationSurfaces::overlaps(const treeBoundBox& bb) const
+bool Foam::conformationSurfaces::overlaps(const boundBox& bb) const
 {
     forAll(surfaces_, s)
     {

applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformationSurfaces/conformationSurfaces.H

@@ -188,7 +188,7 @@ public:
 
             //- Check if the supplied bound box overlaps any part of any of
             //  the surfaces
-            bool overlaps(const treeBoundBox& bb) const;
+            bool overlaps(const boundBox& bb) const;
 
             //- Check if points are inside surfaces to conform to
             Field<bool> inside(const pointField& samplePts) const;