Tidy up some of the parsing of sigcfg.dat files - normalising the errors reported for collections (missing, duplicate and extra items) and simplifying some of the data stored.
Fix a crash on Feather River Route with an undefined light texture being used in a signal type (reports an error and continues with dummy material and config).
git-svn-id: http://svn.uktrainsim.com/svn/openrails/trunk@415 a9f3cfff-6c41-7446-b0ca-052bd761e6eb