content: Fix imported posts (markdown syntax, article types)

The auto-importer has created several issues with the markdown syntax which
needed manual fixing. Additionally quite a lot of event annoucements were
categorized as article.

content/blog/2012/2012-04-04-arduino-workshop-2/index.md

@@ -1,15 +1,13 @@
 ---
 authors:
 - ccchh-archiv
-categories: article
+categories: event
 draft: false
 lastmod: '2012-04-04T20:12:27+02:00'
 publishDate: '2012-04-04T20:12:27+02:00'
 slug: arduino-workshop-2-index
 title: Arduino Workshop
 ---
-![](
-
 Nach unserem ersten [Arduino Workshop im August 2011][1] mit überaus
 positiver Resonanzerreichten uns mehrfach Anfragen bezüglich eines
 erneuten Workshops, den wir hiermit bekannt geben.