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/airport.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg version="1.1" id="airport" xmlns="http://www.w3.org/2000/svg" width="15" height="15" viewBox="0 0 15 15">
+  <path id="path7712-0" d="M15,6.8182L15,8.5l-6.5-1&#xA;&#x9;l-0.3182,4.7727L11,14v1l-3.5-0.6818L4,15v-1l2.8182-1.7273L6.5,7.5L0,8.5V6.8182L6.5,4.5v-3c0,0,0-1.5,1-1.5s1,1.5,1,1.5v2.8182&#xA;&#x9;L15,6.8182z"/>
+</svg>