MFbed:  Update the German documentation set.

doc/de_DE.ISO8859-1/articles/Makefile hook up the new article
doc/de_DE.ISO8859-1/articles/contributing-ports/Makefile new file
doc/de_DE.ISO8859-1/articles/contributing-ports/article.sgml new translation [XX]

Obtained from:  The FreeBSD German Documentation Project.

[XX]:
Translated by: miwi@
Reviewed by: lme@, ds@ (and helper)
Trimmed by: jkois@ ;-)