Add UUID LogicalType

It would be nice to have a `UUID` logical type that could be used for columns containing UUID data. Currently if a user creates a column that contains UUID objects and initializes Woodwork on this column, the UUID data will be converted to a `string` dtype. If this new type is added, we would need to determine whether to continue to store the data as UUID objects or whether to convert these to strings as we do today, but it might be preferable to store these as UUID objects.

Current behavior:
```python
>>> import uuid
>>> import pandas as pd
>>> import woodwork as ww

>>> df = pd.DataFrame({"id": [uuid.uuid4() for _ in range(10)], "vals": range(10)})
>>> df.dtypes
id object
vals int64
dtype: object
>>> type(df['id'][0])

>>> df.ww.init()
>>> df.dtypes
id string
vals int64
dtype: object
>>> type(df['id'][0])

```