PEP8 openbazaar.py through ws.py

PEP8 clean up 3 of 3.  Orders.py has some very deeply nested dictionaries which necessitate long lines.  This situation may suggest minor future refactoring of the affected methods.
A container with zero length evaluates to `False`, so:
```python
if self.db.selectEntries("orders", {"order_id": new_order['id']}):
...
```
If there are other cases of `if len(X) > 0` in the file, please convert them as well.