Make GroupService keep the list of members up to date.

lib/db/api.js

@@ -30,6 +30,12 @@ dbapi.loadUser = function(email) {
   return db.run(r.table('users').get(email))
 }
 
+dbapi.loadGroupMembers = function(email) {
+  return db.run(r.table('devices').getAll(email, {
+      index: 'ownerEmail'
+    })('serial'))
+}
+
 dbapi.saveDeviceLog = function(serial, entry) {
   return db.run(r.table('logs').insert({
     serial: entry.serial