change keyHeader to a more meaningful name

VadereSimulator/src/org/vadere/simulator/projects/dataprocessing/outputfile/TimestepOutputFile.java

@@ -11,6 +11,6 @@ import org.vadere.simulator.projects.dataprocessing.datakey.TimestepKey;
 public class TimestepOutputFile extends OutputFile<TimestepKey> {
 
     public TimestepOutputFile() {
-        super("hdfkh");
+        super("timeStep");
     }
 }