Modified RaceClock to support arbitrary start times

- Amended RaceDataSource interface to require time instead of mark for calculating time.
#story[758]

visualiser/src/main/java/seng302/RaceXMLReader.java

@@ -4,12 +4,11 @@ import javafx.scene.paint.Color;
 import org.w3c.dom.Element;
 import org.w3c.dom.NodeList;
 import org.xml.sax.SAXException;
-import seng302.Model.BoatInRace;
-import seng302.Model.Leg;
-import seng302.Model.Marker;
+import seng302.Model.*;
 
 import javax.xml.parsers.ParserConfigurationException;
 import java.io.IOException;
+import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -272,8 +271,8 @@ public class RaceXMLReader extends XMLReader implements RaceDataSource {
         return legs;
     }
 
-    public GPSCoordinate getMark() {
-        return mark;
+    public ZonedDateTime getZonedDateTime() {
+        return RaceClock.getCurrentZonedDateTime(mark);
     }
 
     public GPSCoordinate getStartPt1() {