Fix file upload

[Vakmeth]

As soon as you upload a new file to cryptopus, the application creates 2 new rows for it. After you are navigated to the file, it is not possible to navigate back. This behaviour has to be fixed.

Acceptance criteria:

• The Fileupload creates only one new row for the generated file
• It is possible to navigate back after the application directs you to the detail-view of the file
• The file-icon of the uploaded file appears directly after the file has been uploaded

[Vakmeth]

It looks like the frontend manages the data wrong, the folder of the created file is always null after it was created, that's the reason we can't navigate back after we get redirected to the file-show component. With the help of @mtnstar I think this can be solved within max 2 days.