WIP : Fix SFTP Plugin of KIO for Windows

Summary:
The fixed plugin works on Windows. Right now, KDE Connect uses it to establish an initial connection over SFTP, which can then be offloaded to any sftp:// handling application.

Currently, this can be achieved seamlessly by using [WinSCP](https://winscp.net) which is a free and open source SFTP Client.

Test Plan:

0. Install WinSCP : https://winscp.net/eng/download.php.

1. set Craft to use `master` for `kio-extras`

```
craft --set version=master kio-extras
```

2. install `kio-extras` and all deps

```
craft -i kio-extras
```

3. apply this patch

4. re-build `kio-extras`

```
craft --compile --install --qmerge kio-extras
```

5. checkout `milestone2` branch from invent.kde.org/piyushaggarwal/kdeconnect-kde

6. build `kdeconnect-kde` again

```
craft --compile --install --qmerge kdeconnect-kde
```

7. Run `kdeconnect-indicator.exe` from within `CraftRoot/bin/`

8. Right  Click on the dark icon in sys tray, go to your phone and click on **Browse Device**.

9. Press YES, followed by an OK on password prompt (the correct password comes pre-filled).

10. Expect WinSCP to take point from there on.

Reviewers: albertvaka, vonreth, sredman, sitter, dfaure

Reviewed By: vonreth, dfaure

Subscribers: pino, andriusr, kde-frameworks-devel, kfm-devel

Tags: #dolphin, #frameworks

Differential Revision: https://phabricator.kde.org/D22105