[WIP] Feature/dashboard

:warning: Unstable, experimental version of dashboard for saleor

Needs improvements.
Here you are translating an already formatted string. This won't work.

Why rely on PKs instead of letting the group define `__str__`?

I would also reformat the indentation for readability:

```python
comment = _(
    'Moved %(how_many)s items %(item)s from group %(old_group)s'
    ' to group %(new_group)s') % {
        'how_many': how_many, 'item': self.item,
        'old_group': self.item.delivery_group, 'new_group': target_group})
```