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/2010/2010-12-15-vortrag-demokratie-braucht-freie-software/index.md

@@ -1,15 +1,14 @@
 ---
 authors:
 - haegar
-categories: article
+categories: event
 draft: false
 lastmod: '2010-12-15T00:34:08+01:00'
 publishDate: '2010-12-15T00:34:08+01:00'
 slug: vortrag-demokratie-braucht-freie-software-index
 title: 'Vortrag: Demokratie braucht Freie Software'
 ---
-![]([Vortrag im Attraktor / Mexikoring
-21, Hamburg][1]\:
+[Vortrag im Attraktor / Mexikoring 21, Hamburg][1]\:
 
 Start 2010/12/15 19:00:00  
  Ende 2010/12/15 21:30:00