ENH: avoid readScalar, readLabel etc from dictionary (#762, #1033)

- use the dictionary 'get' methods instead of readScalar for
  additional checking

     Unchecked:  readScalar(dict.lookup("key"));
     Checked:    dict.get<scalar>("key");

- In templated classes that also inherit from a dictionary, an additional
  'template' keyword will be required. Eg,

     this->coeffsDict().template get<scalar>("key");

  For this common use case, the predefined getXXX shortcuts may be
  useful. Eg,

     this->coeffsDict().getScalar("key");

src/functionObjects/field/nearWallFields/nearWallFields.C

@@ -261,8 +261,8 @@ bool Foam::functionObjects::nearWallFields::read(const dictionary& dict)
     fvMeshFunctionObject::read(dict);
 
     dict.readEntry("fields", fieldSet_);
+    dict.readEntry("distance", distance_);
     patchSet_ = mesh_.boundaryMesh().patchSet(dict.get<wordRes>("patches"));
-    distance_ = dict.get<scalar>("distance");
 
 
     // Clear out any previously loaded fields

src/functionObjects/field/valueAverage/valueAverage.C

@@ -87,7 +87,7 @@ Foam::functionObjects::valueAverage::valueAverage
             if (dict.found(fieldName))
             {
                 const dictionary& valueDict = dict.subDict(fieldName);
-                totalTime_[fieldi] = valueDict.get<scalar>("totalTime");
+                valueDict.readEntry("totalTime", totalTime_[fieldi]);
             }
         }
     }