Reference members for functions-classes
In dune/fufem/functions, several classes exhibit reference members of their BaseTypes or similar, where the BaseType is an interface that only exhibits const methods. I wonder why those classes do not save const reference members.
I do not see anything that interferes with making those references const. Additionally, this avoids a lot of const_cast clutter in my current code.
Examples are ComposedGridFunction, SumGridFunction, their non-grid counterparts and certainly a lot more! Please let me know if you have any objections, if not I will start to provide commits for the dune/fufem/functions classes in the above mentioned manner.