Lifting limits on display options: None vs 0 vs Inf ?
When lifting limits on display options, for some of them one can use `None`:

```
display.max_columns = None
display.display.max_rows = None
display.width = None
```

but for other options, Pandas complains if you use `None` returning `ValueError: Value must have type '<type 'int'>'`, so you have to use 0

```
display.max_col_width = 0
```

Is this intentional? If so, what is the rationale behind it?
