Add "Forgot password" functionality

[letehaha]

To allow users to reset their password

TBD clear requirements

1. Ask users to use email instead of login on the registration stage
2. In the settings let them use username instead of email to perform login action
3. For resetting, add a button on Login page that will redirect to a separate page, send code to email and enter that code to the form to validate user
4. Also add some UI warning if email is not filled (for old users), that email is required to be able to restore the account