Changes to support SMTP auth and SSL

Provides plumbing for additional config to turn on SMTP auth and SSL.

```
email {
        userEnabled = true
        systemEnabled = true
        smtpHost = 'email-smtp.us-east-1.amazonaws.com'
        smtpPort = 465
        smtpUsername = '<REDACTED>'
        smtpPassword = '<REDACTED>'
        smtpSslEnabled = true
        fromAddress = 'asgard@example.com'
        systemEmailAddress = 'asgard@example.com'
        errorSubjectStart = 'ERROR: '
}
```