utf-8 encoding includes BOM to responses

[Weste76]

When for example executing the NLIST command the client receives BOM (0xef 0xbb 0xbf) in front of the received file list
This is in my case interpreted as unicode 0xfeff ('ZERO WIDTH NO-BREAK SPACE').
Resolution would be to use new UTF8Encoding(encoderShouldEmitUTF8Identifier: false) on server side
instead of Encoding.UTF8.