Add pages to invite, edit, and delete users

This takes the original prototype version of this page, and, using the same
fake data (ie nothing is wired up):
- adds an invite users page
- adds an edit (and delete) user page

Both these pages allow the user to set another user’s permissions.

This commit adds images for the ticks and crosses, so we have control over their
appearance.

app/main/dao/services_dao.py

@@ -1,7 +1,7 @@
-from flask import url_for
+from flask import url_for, abort
 from app import notifications_api_client
-from notifications_python_client.errors import HTTPError
 from app.utils import BrowsableItem
+from notifications_python_client.errors import HTTPError
 
 
 def insert_new_service(service_name, user_id):
@@ -29,7 +29,9 @@ def get_service_by_id(id_):
 
 def get_service_by_id_or_404(id_):
     try:
-        return get_service_by_id(id_)
+        return notifications_api_client.get_service(id_)['data']
+    except KeyError:
+        abort(404)
     except HTTPError as e:
         if e.status_code == 404:
             abort(404)