FTP(S) provider - Improvement of error handling

Current Situation

• In some situations (e.g. errors when reading the file size), the original error message is not logged, but is covered by a general YADE error message.
• In addition, there is no information about the file transfer during which the error occurred.

Desired Behaviour

• The YADE error messages should clearly identify the error conditions and forward the messages from the underlying provider.