- Eliminate deprecated annotations and method calls.
- Add required return types to standard methods.
- Add php-cs-fixer rules to improve tests.
- Add .gitignore support for new test result cache.
- Fixed a few minor bugs/bad comments identified while upgrading.

- All files reported by licensecheck[https://metacpan.org/pod/App::Licensecheck] were fixed.

- Adjusted wiki links to point to latest URLs.
- Removed VuFind2 category name (use generic VuFind instead).