Fix styling of the image file upload dialog in gallery

Fix the style of the image file upload dialog in CMS7-8066:

1. Move toolbar to the bottom, beside the "Close" button.
2. Add labels "You can add .." and "Selected files".
3. Change "add files..." to normal button, label: "OK", disable button when uploading is in progress.
4. Replace the "Cancel" buttons beside images to "X" icon.
5. Fix title & its translations.
6. Table containing uploading file:
   • Fix width.
   • Most space reserves for file names: test with long filenames, use CSS ellipse for overflow.
   • Use same styling in previous dialog.
   • use 32x32 px thumbnails, 4px padding around image
7. On errors: messages are displayed below files.
8. On errors: can only close dialog, should not be possible to add more files.
9. Dialog is closed automatically if no error occurs