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/2014/2014-08-27-frappant-sommerfest-2014/index.md

@@ -1,15 +1,13 @@
 ---
 authors:
 - Michael
-categories: article
+categories: event
 draft: false
 lastmod: '2014-08-27T21:36:57+02:00'
 publishDate: '2014-08-27T21:36:57+02:00'
 slug: frappant-sommerfest-2014-index
 title: Frappant Sommerfest 2014
 ---
-![Plakat-Sommerfest-2014\_Druck-460x651](
-
 Auch der CCC Hansestadt Hamburg wird dabei sein mit einem Infostand und
 unserem Junghackertag von 12 bis 16 Uhr, den wir speziell für
 interessierte Kids anbieten.