Using the scalable graphic in place of the static png file saves some ressources in flash and network. It also aligns the filetype to the type announced to the browser. fixes GitHub-issue #5051 Signed-off-by: Sven Roederer <freifunk@it-solutions.geroedel.de> (cherry picked from commit 184e93df5f0365d403d4d7a6243286cbe5b914de)