Refactoring vpu to dbp for file-handling (#2)

packages/file-handling/.gitlab-ci.yml

packages/file-handling/README.md

packages/file-handling/assets/index.html

packages/file-handling/package.json

packages/file-handling/rollup.config.js

packages/file-handling/src/dbp-file-sink.js

packages/file-handling/src/dbp-file-source.js

packages/file-handling/src/dbp-nextcloud-file-picker.js

packages/file-handling/src/demo.js

packages/file-handling/src/file-sink.js

packages/file-handling/src/file-source.js

packages/file-handling/src/i18n.js

packages/file-handling/src/vpu-file-sink.js

packages/file-handling/src/vpu-file-source.js

packages/file-handling/test/unit.js