Dynatrack.cs: Added facilities for refining the profile replication pitch of curves. Optional criteria are chord length and chord displacement from the arc. In either case, if the criterion is exceeded for the default one degree pitch, then a pitch is computed that exactly meets the criterion.
git-svn-id: http://svn.uktrainsim.com/svn/openrails/trunk@687 a9f3cfff-6c41-7446-b0ca-052bd761e6eb