Consider wrapping location in ShootsServer()

Currently, it is required for the user to construct a pyarrow.flight Location object to create a server:

```python
        location = Location.for_grpc_tcp("localhost", self.port)
        return ShootsServer(location, bucket_dir=self.bucket_dir)
```

consider moving this into the constructor, and providing address, port, and bucket_dir as optional params