Simplify implementation for vectors with scalar entries

Using the new Impl::asVector() from dune-common we can get rid of

• several Hybrid::isElse() constructions used to implement special cases for isNumber,
• undefined behaviour invoked by toVector() due to the latter violating strict aliasing rules.

This also removed the dangerous toVector() methods. This is only a partial solution to #63 (closed). We also need to do the same for toMatrix() which requires an analogue Impl::asMatrix() function and a ScalarMatrixView wrapper class.

changed the description

changed the description

assigned to @oliver.sander

changed title from Simplify imeplementation for vectors with scalar entries to Simplify implementation for vectors with scalar entries

added 6 commits

• 5c11a9b6...37311d14 - 3 commits from branch master
• 0e962e10 - Simplify scalar entries in block vector classes
• 36190383 - Add missing include
• d883ca6e - Get rid of toVector()

Compare with previous version

Merging, with a few typo fixes of my own. Thanks!

enabled an automatic merge when the pipeline for d883ca6e succeeds

merged

mentioned in commit 39995de5