Comfort functions for some BaseModel

Idea: provide comfort functions to access model attributes like osw_id, uuid, title and full_title through @property decorators

E.g. here:
[get_osw_id](https://github.com/OpenSemanticWorld-Packages/opensemantic-python/blob/20b5d10f0c3b43b4f7f0a02e54ddc59025d99aee/src/opensemantic/_model.py#L306)

usage:
```python
MyEntity.osw_id
MyEntity.title
MyEntity.uuid
```