Refactor metainfo Packages and references

Metainfo packages are either defined in Python or in custom schemas. Packages in custom schemas are linked to the archive of the entry that they are defined in. To create references towards definitions in a Package, the archive needs to be connected to the Package.

• Packages loaded from mongo are not liked to the respective archive. The qualified_name (with entry_id:...) is preserved, but the upload_id is not. Instead of storing the qualified name, we should rather store upload_id and entry_id in mongo
• metainfo.py is couples to entry_ids, archives, etc. But the metainfo.py is supposed to be independent and such aspects should be moved to datamodel.
• we should replace entry_id:... style qualified names with actual references