Added support for user friendly email addresses as well as dedicated
reply-to addresses for emails being sent by Keycloak.
Both can be customized via the email settings per realm in
the admin-console.
User friendly email addresses use the format:
"Friendly Name"<email@example.org> and provide way to add a meaning
full name to an e-mail address.
We also allow to specify an optional envelope from bounce address.
If a mail sent to a user could not be delivered the email-provider
will sent a notification to that address.
See: https://en.wikipedia.org/wiki/Bounce_address
Add test for proper email headers in sent messages
