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");

applications/test/Function1/Test-Function1.C

@@ -120,8 +120,8 @@ int main(int argc, char *argv[])
         )
     );
 
-    scalar x0 = readScalar(function1Properties.lookup("x0"));
-    scalar x1 = readScalar(function1Properties.lookup("x1"));
+    scalar x0 = function1Properties.get<scalar>("x0");
+    scalar x1 = function1Properties.get<scalar>("x1");
 
     Info<< "Data entry type: " << function1().type() << nl << endl;