Add encrypted password saving with master password

[Entretoize]

I need it so this is my proposal, it saves the host password when entered after having asked for a master password and encrypted the it. Next time it check for existing stored password, decrypt it with the master password and use it. If it fails it ask for a password. It allow to remember only a single password and is secure. It uses aes-256-cbc encryption.

[Entretoize]

New version : https://github.com/Natizyskunk/vscode-sftp/compare/develop...Entretoize:vscode-sftp:patch-3