WIP : CFD-148 create group dashboard

- Created extra ctools plugins to detect the group context.
- Created the group dashboard page.
I would make it less scripted, and also not hardcode the group, maybe something like:

```
Given a group "Dashbaord" with "Public" access is created with group manager "mariecurie"
When I am logged in as user "mariecurie"
Then I should see the group dashboard
```

And then create meta steps that will check:
```
And Group menu item "Home" should be active
And I should see the Quick Post form
And I should see the Activity stream
```