message: tostring: add some docs
diff: @@ -86,3 +86,32 @@ The following section provides a summary of the available functionality for each
  :project: CXX11
  :path: ../../bindings/CXX11/cxx11/
  :members:
  +
  +Debugging
  +---------
  +
  +To help debugging, functionality is provided that creates
  +human-readable representations of adios2 C++11 class instances and
  +enums. To get a string representation, use ``ToString(object)``. You
  +can also directly pass objects to ``ostream``s.
  +
  +Example:
  +
  +.. code-block:: c++
  +
  + auto myVar = io.DefineVariable<double>("myVar");
  + std::cout << myVar << " has shape id " << myVar.ShapeID() << std::endl;
  +
  + // will print:
  + // Variable<double>(Name: "myVar") has shape id ShapeID::GlobalValue
  +
  + if (myVar.ShapeID() != adios2::ShapeID::GlobalArray)
  + {
  + throw std::invalid_argument("can't handle " +
  + ToString(myVar.ShapeID()) + " in " +
  + ToString(myVar));
  + }
  +
  + // will throw exception like this:
  + // C++ exception with description "can't handle ShapeID::GlobalValue
  + // in Variable<double>(Name: "myVar")" thrown
  