Add the possibility to backup maven/NPM packages using the backup rake task

Problem to solve

Currently the backup rake task does not backup maven/NPM packages.

Proposal

Packages should be included into the backup by default, and it should be possible to exclude them if needed in the same way as described in Excluding specific directories from the backup

Links / references

• https://docs.gitlab.com/ee/user/project/packages/maven_repository.html
• https://docs.gitlab.com/ee/user/project/packages/npm_registry.html
• https://docs.gitlab.com/ee/raketasks/backup_restore.html