Move out datengartens into their own section

- /datengarten/index.html returns a blog-like list
- /datengarten/index.ics returns a VCALENDAR
- /datengarten/index.xml returns a schedule.xml-style view

No more pretty rendering includes in the content pages,
some more cleanup in the front matter

layouts/shortcodes/datengarten-infobox.html

@@ -1,19 +0,0 @@
-<p>
-{{ if isset .Page.Params "speaker_url" }}
-<strong><i class="far fa-user fa-fw"></i></strong> <a href="{{ .Page.Params.Speaker_url }}">{{ .Page.Params.Speaker }}</a><br/>
-{{ else }}
-<strong><i class="far fa-user fa-fw"></i></strong> {{ .Page.Params.Speaker }}<br/>
-{{ end }}
-<strong><i class="far fa-calendar fa-fw"></i></strong> {{ dateFormat "02.01.2006, 15:04" .Page.Params.Event_date }} Uhr<br/>
-<strong><i class="fa fa-language fa-fw"></i></strong> {{ .Page.Params.Language }}<br/>
-<strong><i class="fa fa-map-marker fa-fw"></i></strong> {{ partial "location" .Page.Params.Location }}
-</p>
-{{ if isset .Page.Params "recording" }}
-  <p><strong><i class="fa fa-video fa-fw"></i></strong> <a href="{{ .Page.Params.Recording }}">{{ .Page.Params.Recording }}</a></p>
-{{ else }}
-  {{ if and (eq .Page.Params.Streaming true) (not (isset .Page.Params "recording" )) }}
-    <p><strong>Stream:</strong> <a href="https://streaming.media.ccc.de/datengarten">streaming.media.ccc.de/datengarten</a></p>
-  {{ else }}
-    <p><strong><i class="fa fa-exclamation-triangle fa-fw"></i></strong> Dieser Vortrag wird <strong>nicht</strong> gestreamed</a>! / This talk will <strong>not</strong> be streamed!</p>
-  {{ end }}
-{{ end }}

layouts/shortcodes/series.html

@@ -11,7 +11,7 @@
       {{ if eq $art.Params.series $series }}
       <tr>
 	<td>{{ $art.Params.no }}</td>
-	<td>{{ dateFormat "02.01.2006" $art.Params.event_date }}</td>
+	<td>{{ dateFormat "02.01.2006" $art.Params.event.start }}</td>
 	{{ if isset $art.Params "speaker_url" }}
 	<td><a href="{{ $art.Params.speaker_url }}">{{ $art.Params.speaker }}</a></td>
         {{ else }}