do both file and db operations on grouped items

Summary:
This is just a quick fix to be consistent again. It resolves groupes no matter
what, while grouping should be properly handled by views. This manifested in
drag&drop, where groups are not yet handled.

BUG: 375703
FIXED-IN: 5.8.0

Reviewers: #digikam

Differential Revision: https://phabricator.kde.org/D8440