Fix some styling issue in extended tooltip

but the blueimp-gallery css file uses the 'img' path. This css is included in the base mako. See https://github.com/geoadmin/mf-chsdi3/blob/f86a495b6105420f9512a1cde1c57b98d5d98927/chsdi/templates/htmlpopup/base.mako#L24