see also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47226

storage_access() should be deprecated at some point...

E.g. print 1 instead of [1] for scalar vectors, [1 2] instead of [[1 2]]
for matrices with only one row...

If you did rely on `common/logging.hh` to include `common/timedlogging.hh`
your code may not compile anymore.

is_hashable<T>::value is true iff std::hash<T>(T t) works or gcc is too
old

I see no harm in it atm.

-#include <dune/stuff/common/logging.hh>
+#include <dune/stuff/common/timedlogging.hh>
is encouraged, but not mandatory yet