Add config option for gitlab api scope and auto adapt gitlab snippet feature on it

lib/auth.js

@@ -91,6 +91,7 @@ function registerAuthMethod () {
       baseURL: config.gitlab.baseURL,
       clientID: config.gitlab.clientID,
       clientSecret: config.gitlab.clientSecret,
+      scope: config.gitlab.scope,
       callbackURL: config.serverurl + '/auth/gitlab/callback'
     }, callback))
   }