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/airfield.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg version="1.1" id="airfield" xmlns="http://www.w3.org/2000/svg" width="15" height="15" viewBox="0 0 15 15">
+  <path id="path5" d="M6.8182,0.6818H4.7727&#xA;&#x9;C4.0909,0.6818,4.0909,0,4.7727,0h5.4545c0.6818,0,0.6818,0.6818,0,0.6818H8.1818c0,0,0.8182,0.5909,0.8182,1.9545V4h6v2L9,8l-0.5,5&#xA;&#x9;l2.5,1.3182V15H4v-0.6818L6.5,13L6,8L0,6V4h6V2.6364C6,1.2727,6.8182,0.6818,6.8182,0.6818z"/>
+</svg>