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/rigidBodyDynamics/pendulumAndSpring/pendulumAndSpring.C

@@ -55,7 +55,7 @@ int main(int argc, char *argv[])
     // Create the pendulumAndSpring model from dictionary
     rigidBodyMotion pendulumAndSpring(runTime, pendulumAndSpringDict);
 
-    label nIter(readLabel(pendulumAndSpringDict.lookup("nIter")));
+    label nIter(pendulumAndSpringDict.get<label>("nIter"));
 
     Info<< pendulumAndSpring << endl;
     Info<< "// Joint state " << endl;