Inasafe Wizard for keywords creation

Here is a new version, PEP-257 compliant. One doubt is a docstring like that: 

``` python
        """Automatic slot executed when category change.

        Set description label and subcategory widgets according
        to the selected category
        """
```

Should I swap the first and third line? And change "change" to "changes"? ;-)
I was trying to follow the existing code, so I'm unsure which first-line information will be more consistent with the present documentation.