picked up by a copyright change.

Creates linear slope only from low and high elements around the sample
value, so rate will be discontinuous.  Would be better with higher
order gradient calculation.

STYLE: use findIndices instead of findAll for coordinateSystems

- aspect ratio and cellDeterminant do not use 3rd direction
- wedges are properly check for having opposite one

- findAll() method returns a labelList of all matching names
- find() method returns the index to the first matching name

  For example, use a regex to specify alternative coordinate systems
  in porousZones
  (
      "cat1?(Back|Front)*"
      {
          coordinateSystem    "(cat1|system_10)";
          porosity    0.781;
          ...
      }
  )

- allows a regex to collect several cellZones.
  For example,
  (
      "cat1?(Back|Front)*"
      {
          coordinateSystem    system_10;
          porosity    0.781;
          ...
      }
  )

Adapted meshSearch and sampledTriSurfaceMesh to use it.

- as per commit 937e0d23

- reflects commit 583d518a