KItemModels: Convert license headers to SPDX markers
Summary:
Convert license headers to SPDX markers and add REUSE.software
compliant licesne files. This update also includes several copyright holder
clarifications for contracted contributors, where only implicitly the
copyright for the authors was stated inside the copyright statement of
the company.
Reviewers: dfaure, cgiboudeaux
Reviewed By: cgiboudeaux
Subscribers: cgiboudeaux, kde-frameworks-devel
Tags: Frameworks
Maniphest Tasks: T11550
Differential Revision: https://phabricator.kde.org/D27103