Fix constructors in iterators

This is a replacement for !580 (closed)

This issue is that some iterators, e.g. the RealIterator in base_array define a copy constructor but no copy assignment operator. This will not be supported in the future, I think. So, this MR adds corresponding assignment operators alongside the constructors. The difficulty is that these iterators actually accept copy from other iterators of different template types. This needs to be taken into account. Maybe there is a simpler solution to the templated and constrained constructors.

mentioned in merge request !580 (closed)

changed the description

changed milestone to %DUNE 2.11.0

requested review from @markus.blatt

approved this merge request

We might want to mark constructors with a single argument as explicit. As this is a larger change affecting many more places, I would refrain this before 2.10.

approved this merge request

Looks OK to me.

resolved all threads

added 21 commits

• c1b8413b...43a98e67 - 20 commits from branch master
• 1f896e2a - Fix constructors in iterators

Compare with previous version

resolved all threads

marked this merge request as ready

merged

mentioned in commit 26699c4b

picked the changes into the branch cherry-pick-26699c4b with commit 925ff5ed

mentioned in commit 925ff5ed

mentioned in merge request !597 (merged)