40C3: tours, schedule data, tour map and calendar entries

- tour-map shortcode: Leaflet map of the tour locations with routes from the
  Congress, from the map/tours sections of data/schedule/<event>.yaml; Leaflet
  and the OSMIC, Maki and Temaki icon sets vendored; 39C3 uMap data converted.
- calendar shortcode: per tour date, a pill with an .ics download (iCalendar)
  and a Google Calendar link; Font Awesome Free vendored, fa-icon partial.
- README sections for the calendar and tour map shortcodes and the map data.

assets/vendor/icons/maki/mountain.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg height="15" viewBox="0 0 15 15" width="15" xmlns="http://www.w3.org/2000/svg" id="mountain">
+  <path d="m7.5 1c-.3 0-.4.2-.6.4l-5.8 9.5c-.1.1-.1.3-.1.4 0 .5.4.7.7.7h11.6c.4 0 .7-.2.7-.7 0-.2 0-.2-.1-.4l-5.7-9.5c-.2-.2-.4-.4-.7-.4zm0 1.5 3.3 5.5h-.8l-1.5-1.5-1 1.5-1-1.5-1.5 1.5h-.9z"/>
+</svg>