[dune-fem] Bug in jacobianAll

[Agnese, Marco]

Hi Martin,
thank you very much for the detailed explanation. 
I was aware of the copyable entities/intersections change but I hadn't thought about the implications.

Now I am using in my code the range based for which seems a more concise and elegant way to solve this issue.

One final question, performance wise, is better to use

for(const auto entity: space)

or

for(const auto& entity:space) ?

You said that might be some difference for some grid overloading the copy constructor, therefore I assume that the first should be preferred.Am I right?

Thank you very much,
cheers,
Marco.