Merge branch 'minor-array-handle-changes' into 'master'

Some minor changes to fancy array handles.

This are just some minor things I ran into while documenting these classes.
One change is just an error in a comment. The other change allows you
to specify the type in make_ArrayHandleCast as a template argument instead
of creating an instance.

See merge request !388

vtkm/cont/ArrayHandleCast.h

@@ -77,7 +77,7 @@ public:
 template <typename T, typename HandleType>
 VTKM_CONT_EXPORT
 ArrayHandleCast<T, HandleType> make_ArrayHandleCast(const HandleType &handle,
-                                                    const T&)
+                                                    const T& = T())
 {
   return ArrayHandleCast<T, HandleType>(handle);
 }

vtkm/cont/ArrayHandleConstant.h

@@ -70,7 +70,7 @@ public:
     : Superclass(detail::ConstantFunctor<T>(value), numberOfValues) {  }
 };
 
-/// make_ArrayHandleImplicit is convenience function to generate an
+/// make_ArrayHandleConstant is convenience function to generate an
 /// ArrayHandleImplicit.  It takes a functor and the virtual length of the
 /// array.
 ///