FTP improvements

- add a setting to require TLS
- add symlink support

require TLS 1.2 for all TLS connections

webdavd/server.go

@@ -61,6 +61,7 @@ func (s *webDavServer) listenAndServe() error {
 	if s.certMgr != nil {
 		httpServer.TLSConfig = &tls.Config{
 			GetCertificate: s.certMgr.GetCertificateFunc(),
+			MinVersion:     tls.VersionTLS12,
 		}
 		return httpServer.ListenAndServeTLS("", "")
 	}