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/OpenFOAM/primitives/functions/Function1/ramp/ramp.C

@@ -30,7 +30,7 @@ License
 void Foam::Function1Types::ramp::read(const dictionary& coeffs)
 {
     start_ = coeffs.lookupOrDefault<scalar>("start", 0);
-    duration_ = coeffs.get<scalar>("duration");
+    coeffs.readEntry("duration", duration_);
 }