Refactoring

Refactoring

* Refactoring:
** usage of the dart feature "late": many "Type? x;" replaced by "late TYPE x;"

* module_meta_data:
** new module attribute needsSqlAll:
   creates a "all" section of the module with no WHERE condition
** Fix in pageByName(): "nothing found" is handled now correctly
** Fix in primaryOf(): "nothing found" is handled now correctly

* rest_server:
** logging of the using configuration file