Two factor authentication

### Issue type

**I'm submitting a ...** (check one with "x")

* [ ] bug report
* [x] feature request

### Issue description

**Current behavior:**
No possibility for using two factor authentication with NbPasswordAuthStrategy

**Expected behavior:**
Extend NbPasswordAuthStrategy or create new one with two factor authentication. For example:
1. user inputs login with password, server verifies login and password and sends sms code to user
2. user gets sms code and input it, server verifies sms code and sends response with JWT token
3. redirect to home page if success