- Importing entity
- Deepening an entity
- Object tools for entity change list

- Added link to deepen item in its change view.
- Moved most logic around importing items into wb_utils.

Added 'extra_data'-field to models that hold a value: EntityClaim, EntityClaimQualifier, EntityClaimReferenceClaim to support storing data on more complex values, like dates with precision and quantities with units. Adjusted fetch_data script.