Removed Program.RealTime and replaced with Viewer.RealTime.
Added Simulator.GameTime.
Both Viewer.RealTime and Simulator.GameTime are monotonically increasing values; unlike Simulator.ClockTime, neither will jump when the user skips time forwards or backwards. All non-activity events should use one or other of these new times.
git-svn-id: http://svn.uktrainsim.com/svn/openrails/trunk@446 a9f3cfff-6c41-7446-b0ca-052bd761e6eb