ENH: make 'planeType' optional for dictionary construct of a plane

- simpler to write for sampled cutting planes etc.
  For example,

      slice
      {
          type        cuttingPlane;
          point       (0 0 0);
          normal      (0 0 1);
          interpolate true;
      }

  instead of

      slice
      {
          type        cuttingPlane;
          planeType   pointAndNormal;
          pointAndNormalDict
          {
              point   (0 0 0);
              normal  (0 0 1);
          }
          interpolate true;
      }

STYLE: add noexcept to some plane methods

tutorials/verificationAndValidation/atmosphericModels/atmDownstreamDevelopment/setups.orig/common/system/samplePlanes

@@ -12,14 +12,10 @@ samplePlanes
     {
         planes
         {
-            type        cuttingPlane;
-            planeType   pointAndNormal;
-            pointAndNormalDict
-            {
-                point   (1e-8 0 0);  // slightly inside the domain
-                normal  (1 0 0);
-            }
+            type    cuttingPlane;
 
+            point   (1e-8 0 0);  // slightly inside the domain
+            normal  (1 0 0);
             offsets ( 500 1000 1500 2000 2500 3000 3500 4000 4500 );
         }
     }