ENH: improve dimensions handling for setExpr* utilities (#2014)

- new '-ascii' option to write in ASCII format instead of the
  controlDict setting. This can be useful when generating fields that
  should be parsed with other tools, or for visual inspection.

- correct mismatch of option names and lookups

tutorials/incompressible/simpleFoam/turbineSiting/system/setExprBoundaryFieldsDict

@@ -25,7 +25,7 @@ updateBCs
     {
         target      value;
         variables   ( "rho=1.2" );
-        expression  #{ 0.5*rho*cbrt(mag(U)) #};
+        expression  #{ 0.5*rho*pow(mag(U),3) #};
     }
 
     expressions

tutorials/incompressible/simpleFoam/turbineSiting/system/setExprFieldsDict

@@ -20,7 +20,8 @@ readFields      ( U );
 _value1
 {
     variables   ( "rho=1.2" );
-    expression  #{ 0.5*rho*cbrt(mag(U)) #};
+    expression  #{ 0.5*rho*pow(mag(U),3) #};
+    dimensions  [ kg s^-3 ];
 }
 
 expressions