.upsert() with hash_id throws error

```python
db[table_name].upsert_all(rows, hash_id="pk")
```
This throws an error: `PrimaryKeyRequired('upsert() requires a pk')`

The problem is, if you try this:

```python
db[table_name].upsert_all(rows, hash_id="pk", pk="pk")
```
You get this error: `AssertionError('Use either pk= or hash_id=')`

`hash_id=` should imply that `pk=` that column.