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/ice-cream.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="15" height="15" viewBox="0 0 15 15" id="ice-cream">
+  <path d="M5.44,8.17a3.473,3.473,0,0,0,2-.63A3.5,3.5,0,0,0,9,8.14h.44L8,13.7a.5.5,0,0,1-.92,0Zm6-3.473a2,2,0,0,1-4,0h0a2,2,0,1,1-2-2h.12a2,2,0,1,1,3.75,0h.13A2,2,0,0,1,11.439,4.7Z"/>
+</svg>