Add a ‘See dashboard’ permission

Our research and prototyping around ‘basic view’ found that:
- a lot of users who send messages rarely or never look at the dashboard
  (yet it’s the first page they see when they sign in)
- team managers like the idea of taking away things that users don’t
  need in order to make the interface simpler

We’ve disentangled the simpler way of sending messages from being part
of ‘basic view’. This means we can give managers the option of taking
away the dashboard as an independent choice, not something that’s
wrapped up in a separate ‘view’.

I think that this checkbox is a more straightforward proposition than
‘basic view’ ever was (despite all the work we did to explain it and
develop the nested checkbox pattern). In research users would often
explain the feature back to us as being about hiding the dashboard – we
should try to make Notify operate in terms of concepts that come
naturally to people wherever possible.

app/notify_client/models.py

@@ -197,7 +197,7 @@ class InvitedUser(object):
         return set(self.permissions) > set(permissions)
 
     def has_permission_for_service(self, service_id, permission):
-        if self.status == 'cancelled' and permission != 'view_activity':
+        if self.status == 'cancelled':
             return False
         return self.service == service_id and permission in self.permissions