Change default exercise author to hostname
Change default exercise author to hostname

This is a fix for issue #159.

Previously, if the administrator did not specify an author when
creating a new exercise, the author would default to ‘wger.de’. Now, if
the administrator does not specify an author for a new exercise, the
author will default to the hostname that WGER is installed on.

petervanderdoes/wger,kjagoo/wger_stark,DeveloperMal/wger,rolandgeider/wger,wger-project/wger,kjagoo/wger_stark,wger-project/wger,petervanderdoes/wger,petervanderdoes/wger,wger-project/wger,wger-project/wger,kjagoo/wger_stark,kjagoo/wger_stark,petervanderdoes/wger,DeveloperMal/wger,DeveloperMal/wger,DeveloperMal/wger,rolandgeider/wger,rolandgeider/wger,rolandgeider/wger