CHG: User and system interaction to its own class, process all events per frame, not just one

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6794 8aca7d54-2c30-db11-9de9-000461428c89
fixed documentation

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6795 8aca7d54-2c30-db11-9de9-000461428c89