SftpPathNotFoundException doesn't contain the errored path #567

It is weird to debug an error throwing a Renci.SshNet.Common.SftpPathNotFoundException exception since it doesn't actually say what the path was.

It should be trivial to add another property to the SftpPathNotFoundException class and assign it in the constructor. Preferably the argument shouldn't be optional though.

Exception in my specific case is thrown from here:

Renci.SshNet.Common.SftpPathNotFoundException: No such file
     at Renci.SshNet.Sftp.SftpSession.RequestOpenDir(String path, Boolean nullOnError)
     at Renci.SshNet.Sftp.SftpSession.ChangeDirectory(String path)
     at Renci.SshNet.SftpClient.ChangeDirectory(String path)
     at <my code>

Finding the bug in my code isn't too hard, just requires me to add some more/better exception handling and logging of my ChangeDirectory call.