Make deleting individual images after uploading more intuitive

[zabak]

At least add something like "Reload page to delete unwanted images"
Better: make it behave more like filesender.cesnet.cz: after dragging a set of documents inside the rectangle, they are uploaded and they appear above the rectangle with a "-" button beside them.

[zabak]

Please move the list of uploaded images above the image upload rectangle so that they are not hidden below the edge of the screen.