Added constructor overload for use in deriving switch geometry - I might choose to do this derivation differently in the very near future.
Added some initial switch geometry calculations. I suspect there's an easier way to do this, though.
Added interlocking and movement authority classes.
git-svn-id: http://svn.uktrainsim.com/svn/openrails/trunk@505 a9f3cfff-6c41-7446-b0ca-052bd761e6eb