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 would collapse that into a single list comprehension:
```
for m in [m for m in modules if m.category.data == 'container']:
   ...
```