SkyView: Unify stale check for loading the history

When loading the history, the check for stale aircraft tracks is done
differently.
This results in lots of dotted/stale track after opening the web page.
Improve this by using the same 5 second timeout stale criterion to
postions loaded from history. Add an additional check to better detect
stale tracks when loading history positions that are spaced 30 seconds
apart.

public_html/script.js

@@ -444,7 +444,7 @@ function end_load_history() {
                         console.log("Updating tracks at: " + now);
                         for (var i = 0; i < PlanesOrdered.length; ++i) {
                                 var plane = PlanesOrdered[i];
-                                plane.updateTrack((now - last) + 1);
+                                plane.updateTrack(now, last);
                         }
 
                         last = now;