Update index.html

https://github.com/duplicati/duplicati/issues/1145
Cleanup for issue #1149 and more subtle style for the headers.
Update index.html

add footer.
Update main.css

add css for footer
Update index.html

change footer with css
Fix for older versions of Mono, fixes issue #1136.
Merge branch 'patch-3' of https://github.com/sfahrenholz/duplicati
Merge branch 'patch-4' of https://github.com/sfahrenholz/duplicati
Merge branch 'patch-5' of https://github.com/sfahrenholz/duplicati