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/tunnel.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="15" height="15" viewBox="0 0 15 15" xmlns="http://www.w3.org/2000/svg" id="tunnel">
+  <path d="M4 2C2.34315 2 1 3.32706 1 4.96406V12.012C1 12.5576 1.44772 13 2 13H3V8.55391C3 6.09839 5.01472 4.10781 7.5 4.10781C9.98528 4.10781 12 6.09842 12 8.55393V13H13C13.5523 13 14 12.5576 14 12.012V4.96406C14 3.32706 12.6569 2 11 2H4ZM11 10V9.04794C11 6.86526 9.43299 5.09583 7.5 5.09583C5.56701 5.09583 4.00001 6.86526 4 9.04794V13L11 10Z"/>
+</svg>