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.

layouts/_partials/fa-icon.html

@@ -0,0 +1,10 @@
+{{- /*
+A Font Awesome icon as inline SVG, decorative (hidden from screen readers) and drawn in the
+current text colour. Param: the icon as "style/name", e.g. "regular/calendar-plus"; the files
+are in assets/vendor/fontawesome/. The SVG keeps its attribution comment (CC BY 4.0).
+*/ -}}
+{{- with resources.Get (printf "vendor/fontawesome/%s.svg" .) -}}
+  {{- replace .Content "<svg " `<svg class="fa-icon" aria-hidden="true" focusable="false" ` 1 | safeHTML -}}
+{{- else -}}
+  {{- errorf "fa-icon: no icon %q in assets/vendor/fontawesome/" . -}}
+{{- end -}}