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/2006/2006-03-08-machackers-treffen-2/index.md

@@ -1,7 +1,7 @@
 ---
 authors:
 - desc
-categories: article
+categories: event
 draft: false
 lastmod: '2006-03-08T19:19:36+01:00'
 publishDate: '2006-03-08T19:19:36+01:00'
@@ -25,4 +25,3 @@ ist ein Treffen im 2-Wochen-Takt (08.03. / 22.03. / 05.04. / 19.04. /
 * Kennenlernen
 * OLSR - wie bekomme ich es mac-like und in die Systemeinstellungen
   (Ideensammlung und Vorstellung des OLSR)
-