Use yaml.safe_ functions

[reneburghardt]

Replace yaml.dump and yaml.load with yaml.safe_dump and yaml.safe_load to avoid emitting and parsing Python-specific object tags. This improves security (prevents arbitrary object construction on load) and ensures YAML files remain portable and standards-compliant while it should still be working well for our use case as we only need standard Python objects in our meta files.

[Vrittigyl]

Hi, I'd like to work on this issue, could you assign this to me.

[reneburghardt]

Thanks a lot @Vrittigyl