Make user model return a service model, not JSON

This makes it:
- nicer, by having access to sensibly named things like
  `Service.trial_mode` instead of `service['restricted']`.
- less likely to write Jinja code like `service.trail_mode`, which would
  fail silently if `service` was a dictionary

app/models/service.py

@@ -56,7 +56,6 @@ class Service(JSONModel):
     def __init__(self, _dict):
 
         super().__init__(_dict)
-
         if 'permissions' not in self._dict:
             self.permissions = {'email', 'sms', 'letter'}
 
@@ -94,6 +93,10 @@ class Service(JSONModel):
     def trial_mode(self):
         return self._dict['restricted']
 
+    @property
+    def live(self):
+        return not self.trial_mode
+
     def has_permission(self, permission):
         return permission in self.permissions