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/2018/2018-02-09-wir-steppen-34c3-vortraege-in-vektoren/index.md

@@ -1,7 +1,7 @@
 ---
 authors:
 - jen
-categories: article
+categories: event
 draft: false
 header:
   caption: Sorry this blog entry was migrated, there is no Alt-Text
@@ -13,8 +13,9 @@ tags:
 - event
 - congress
 - social
-title: "Wir steppen 34c3-Vortr\xE4ge in Vektoren"
+title: "Wir steppen 34c3-Vorträge in Vektoren"
 ---
+
 Wir wollen zusammen einige Vorträge vom 34c3 schauen. Deshalb laden
 wir herzlichst ein am Freitag den 09.02. ab 18:00 in unserem Raum
 daran teilzunehmen.