add support for multiple bindings

Fixes #253

httpd/httpd.go

@@ -2,7 +2,7 @@
 // REST API allows to manage users and quota and to get real time reports for the active connections
 // with possibility of forcibly closing a connection.
 // The OpenAPI 3 schema for the exposed API can be found inside the source tree:
-// https://github.com/drakkan/sftpgo/tree/master/api/schema/openapi.yaml
+// https://github.com/drakkan/sftpgo/blob/master/httpd/schema/openapi.yaml
 // A basic Web interface to manage users and connections is provided too
 package httpd