removed ost::Message / removed prefix from ost::Error / added exception translation for ost:error to base and removed exception translations in img and info modules / removed some try:/except: clauses in gui pymod scene scripts by using InfoGroup::RetrieveGroup

git-svn-id: https://dng.biozentrum.unibas.ch/svn/openstructure/trunk@2703 5a81b35b-ba03-0410-adc8-b2c5c5119f08