let user customize colors

In the upper left is a details-tag containing color inputs which allow the user
to change all colors. The chosen colors are stored in the local storage and
restored from there on every page load. There's also a reset link, removing all
colors from the local storage and reloading the site.
fix hovering of visible ranking table

!important is evil. Probably best to get rid of it.
removed dead links to twitch
embed twitch videos too

The youtube player is removed from DOM when the twitch player is starting, and
vice versa. Just hiding with display='none' didn't work and twitch seems to
buffer all the time, so it's best to get rid of it.
always scroll player

This way it prevents jumping up to the border when clicking on the first link
(in 2-column-layout).