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/finiteArea/faMesh/faPatches/constraint/processor/processorFaPatch.H

@@ -160,8 +160,8 @@ public:
         )
         :
             coupledFaPatch(name, dict, index, bm),
-            myProcNo_(readLabel(dict.lookup("myProcNo"))),
-            neighbProcNo_(readLabel(dict.lookup("neighbProcNo"))),
+            myProcNo_(dict.get<label>("myProcNo")),
+            neighbProcNo_(dict.get<label>("neighbProcNo")),
             neighbEdgeCentres_(),
             neighbEdgeLengths_(),
             neighbEdgeFaceCentres_(),