Co-authored-by: Martin Hierholzer <martin.hierholzer@desy.de>

Co-authored-by: Martin Hierholzer <martin.hierholzer@desy.de>

DeviceManagers which are accessing the same backends under the hood are grouped.
Each recovery groups opens devices in three stages. It concludes a stage for all devices before starting with the next one.
1. (Re)-Open the devices
2. Run the initialisation handlers
3. Write the recovery accessors

update project template

This allows us to use target_compile_features to set the C++ standard
in cppext and move to a newer standard.