Create/edit dashboards with sections

Enables the creating and editing of dashboards with sections.

Should be deployed along with the sectioned-modules branch in stagecraft.

Story: https://www.agileplannerapp.com/boards/15088/cards/7652
I was initially confused by this which is entirely my problem. Just wondering if some really simple tests for this any the visualisation choices function would be good though? I think it was the next at the end confusing me. Apparently you can also do:

```
next(module for module in self.get_types() if module["name"] == "section")
```

Which reads slightly better to me (but I am a bit of a python dunce).