Upgrade to the latest Bootstrap theme
get_involved: Fix typo
conf: Use new options fron Bootstrap
css: Adapt our customization to the new Bootstrap
layout: Remove the global TOC container

We now have proper links in the top bar!
css: Make the admonitions slightly nicer
Add a sidebar for the FAQ

We also need to make the page content slightly wider.
Add TOCs to install and get_involved
css: Redo the style

Our changes were causing problems with the sidebars/TOCs, so let's go
back closer to the defaults.

The theme does look much nicer now in its latest version than before, so
we don't need to customize the pages so heavily anyway.
css: Add some margins around the admonitions
faq: Drop now invalid notice
faq: Shorten a subtitle a bit
index: Fix license

Oops... :-/
index: Be honest about our current state