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/farm.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="farm">
+  <path d="m8 6-3-2-3 2-1 2v4h2v-2h4v2h2v-4zm-2 2h-2v-2h2zm8 4h-3v-9.5c0-.39782.158-.77936.4393-1.06066s.6629-.43934 1.0607-.43934.7794.15804 1.0607.43934.4393.66284.4393 1.06066z"/>
+</svg>