Deleted code is either no longer needed as it does not match the grml
based environment or it conflicts/overwrites grml zsh settings.

The cache directory is now in ~/.cache/oh-my-zsh

The zsh-navigation-tools plugin is no longer used.

Bugs fixed:

  * $PATH could land up with duplicates in it
  * HIST_STAMPS was in the wrong format

At some point the contents $DESKTOP_SESSION of changed in Kubuntu. This
change supports both the old and the new.

The prompt before this point is '%n@%m:%~%#', so the deleted script no
longer does anything useful and is a potential issue for anyone using
an alternate theme.

As it was causing an error.

Fixed konsole and kitty not displaying fonts when system fonts
are based on nerd-fonts v2.0.0

As it was causing an error.

Fixes issue #1