Bug 25941: Reindent Upload local cover image page

Bug 25941: Reindent Upload local cover image page

This patch reindents the "Upload local cover image" template to make
indentation consistent. Some lines have been split up. Some markup
inconsistencies have been corrected.

To test, apply the patch and enable the LocalCoverImages system
preference.

- Go to Tools -> Upload local cover image.
- Test uploading single images or ZIP files of images.
- Confirm that everything works as expected.

Use your preferred method for checking the differences between files
while ignoring whitespace. I use diff with the  "-w" flag, but I'm not
some kind of diff deity. The only changes you see should be split lines.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>