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/2007/2007-11-19-bildungswerk-hamburger-wahlstift/index.md

@@ -1,7 +1,7 @@
 ---
 authors:
 - ccchh-archiv
-categories: article
+categories: event
 draft: false
 lastmod: '2007-11-19T12:11:02+01:00'
 publishDate: '2007-11-19T12:11:02+01:00'
@@ -12,7 +12,6 @@ Am **Mittwoch**, dem **21.11.2007** ab ca. **19:00 Uhr** berichtet Jens
 im Rahmen des Hamburger Bildungswerkes über die Technik hinter dem
 Hamburger Wahlstift.
 
-
 * [Übersicht zum Bildungswerk][1]
 * [Anfahrtsbeschreibung][2]