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/viewpoint.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg id="viewpoint" xmlns="http://www.w3.org/2000/svg" width="15" height="15" viewBox="0 0 15 15">
+  <path id="cf3b542b-d2af-4732-9b92-9e3dc05e460f" d="M6.02,8.425a2.3859,2.3859,0,0,0-.46.44l-4.55-3.5a7.9976,7.9976,0,0,1,1.51-1.51Zm6.46-4.56-3.5,4.55a2.3971,2.3971,0,0,1,.45.45l4.56-3.5A7.945,7.945,0,0,0,12.48,3.865ZM7.3042,10.0129a1.5,1.5,0,1,0,1.6829,1.2914h0A1.5,1.5,0,0,0,7.3042,10.0129ZM6.43,2.235a7.9329,7.9329,0,0,0-2.06.55l2.2,5.32a2.0438,2.0438,0,0,1,.61-.17Zm2.14.01-.75,5.69a2.49,2.49,0,0,1,.61.16l2.2-5.3A7.2129,7.2129,0,0,0,8.57,2.245Z"/>
+</svg>