db modules should return hashes and lists with subtype auto

[davidnich]

they are returned untyped lists and hashes which enforces type stripping when the values are used as the basis for a new list or hash

[davidnich]

one problem is the abstract base classes were developed before complex types were implemented and have return types like list and hash

the best solution will probably be to make it a warning instead of an error to have a mismatched return type like hash for a base type like hash<auto> and change both the return types in the abstract classes and the modules at the same time