Luca google scoped login (#805)

* Fixed auth enforcer so uses plugins if available

* This works

* Better doc

* Fixed one more case

* whoops

* Renamed internal members to have a _ in front

* Fixed problem with credentials being too long

py4web/utils/auth_plugins/oauth2google_scoped.py

@@ -71,7 +71,7 @@ def _define_tables(self):
             Field('email'),
             Field('name'), # First and last names, all together.
             Field('profile_pic'), # URL of profile pic.
-            Field('credentials') # Credentials for access, stored in Json for generality.
+            Field('credentials', 'text') # Credentials for access, stored in Json for generality.
         ])