[RFE] Read peer password from file

[Oleksandr Natalenko]

Hello.

Separating configuration and credentials is always appreciated. Given there's PrivateKeyPath now, similarly, it should be possible to read peer password from a file. For instance:

"tls://1.2.3.4:1234?password_file=/etc/credstore/yggdrasil/peer1.password"

Please consider.

Thanks.