Integration of vpu-file-source and implementation of queuing and uploading for qualified signing (#28)

This reverts commit fd770eca.

The scale factor was used to restore the previous position. Not sure
why it's needed, but revert for now.

The original plan was to move the non-page-position related buttons into
a new line, but this looked very unstructured. This moves them to the edge
and centers the page position ones instead.

So it's clear that the signature gets rotated and not the PDF

See #25

See issue #27

And an ugly JS error

Fixes #24

and not just as a filename with a magic base path

Make it independent of the border width and block width/height.

See #14

It's an implementation detail