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/tour-map-icon.html

@@ -0,0 +1,20 @@
+{{- /*
+Returns a map icon as a data: URI, or "" if there is none by that name.
+The name is looked up in the vendored icon sets in assets/vendor/icons/, in the order
+osmic, maki, temaki; a prefix like "maki:garden" picks the set.
+*/ -}}
+{{- $name := . -}}
+{{- $sets := slice "osmic" "maki" "temaki" -}}
+{{- with findRESubmatch `^(osmic|maki|temaki):(.+)$` . 1 -}}
+  {{- $sets = slice (index . 0 1) -}}
+  {{- $name = index . 0 2 -}}
+{{- end -}}
+{{- $uri := "" -}}
+{{- range $sets -}}
+  {{- if not $uri -}}
+    {{- with resources.Get (printf "vendor/icons/%s/%s.svg" . $name) -}}
+      {{- $uri = printf "data:image/svg+xml;base64,%s" ((. | minify).Content | base64Encode) -}}
+    {{- end -}}
+  {{- end -}}
+{{- end -}}
+{{- return $uri -}}