Preliminary swipe support

Cleanup and bugfixes needed.
Quick and dirty overlay
mobile web css
about page css
fixed position of close button in overlay (sorta), also practising committing changes when Juliusz is not around.
close icon for about overlay.
content for about overlay.
minor styling changes for about overlay.
Fix swiping, kind of
Further improvements to swiping

Don't allow scrolling while swiping, don't swipe if scrolled.
new icons!
Clean up CSS a bit
Go back to scrollable div for mobile version

Desktop version will use normal full-page vertical scrolling in future
patches.
Use vertical full-page scrolling on desktop

Also a bit of a cleanup. In a future patch, scroll images when card
changes too.