Show version number, configured URLs, add button that redirects to the portal to change the upload slot

[kursawero]

it would be useful, if in uploader one can see in GUI the version number
as well as configured backendUrls. Or having an info button that
displays those to verify (do we have access to git commit hash?).

during testing I find that it would be also useful to squeeze somewhere
button that would redirect back to portal upload slot selection (like we
do after upload finish). In case user finds that he opened wrong slot
for upload he may want to go back to slot selection (DICOM tab in
Subject/Events/DICOM view)