Revised demo game.  Weight limits on tracks, roads, and bridges are now (finally) appropriate for all lines.  All lines are "real" (the phony long-distance line now goes somewhere).  City limits are sane.  Border slopes modified to eliminate old "slope to edge of map".  Increased variety of houses to show off pak better.  Roads in city are city roads not public player roads.  Signal system does not get anything stuck.  Added sidings in the mountains.
Increase maximum_intransit_percentage to make long ship routes work properly.
Merge branch 'ncn-devel' of http://github.com/neroden/simutrans-pak128.britain.git