Logging Project: Define Python API for logging-enabled `Codelist`

Follow on to #58 and #59 

**Goal:** Support logging via the Python bindings with a simple API.

Example:

```python
c = CodeList("Pneumonia", "ICD10", "Manually created", logging=True)
```

**Scope:**

- Add optional logging=True parameter to Python CodeList constructor but set this as default True.
- Expose method to retrieve logs from Python, e.g. `c.get_log()`