Slightly reworked loading screen with more status messages during creation

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6406 8aca7d54-2c30-db11-9de9-000461428c89
Merge commit 'f1b7f' into merge-from-standard

Conflicts:
	besch/reader/obj_reader.cc
	dataobj/network_cmp_pakset.cc
	simloadingscreen.cc
	simworld.cc
	simworld.h