keep and use "Lang" directive in awstats config files
awstats config files are deleted and newly generated every time the cronjob runs. by now all changes/additions to these files are lost.
with these changes the language setting is retained for each site: the "Lang" parameter from awstats.DOMAIN.conf is read before it gets deleted and will be added to the content before the new config file is written. also, the "-lang" parameter is removed from the awstats-command, so the global value for "Lang" in awstats.conf.local or the value in awstats.DOMAIN.conf will be respected. Closes #3668