ENH: support find via keyType for coordinateSystems

- 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;
          ...
      }
  )