[Howto] Fix warnings about deprecated LaTeX macros
[Bugfix][Howto] Work around abug in the interaction between KOMAScript and headings

The current version of KOMAScript has a bug when used together with the
headings package. The recommnded fix according to

http://tex.stackexchange.com/questions/166779/koma-script-throws-extra-else-error

is to replace the headings package with the command
\pagestyle{useheadings} as provided by KOMAScript.
[Howto] Fix compilation problem in beamer mode
[Cleanup] Fix trailing whitespace in Howto TeX files