Preserve graph options when clicking d3 nodes (#2139)

When clicking a d3 node, the new url was built up with a static set of
options, clearing out things like hide done and invert. This means the
graph would flip or gain lots of nodes when you click a link. In order
to better preserve the options, we now simply change the taskId in the
current URL.

luigi/static/visualiser/js/visualiserApp.js

@@ -486,7 +486,8 @@ function visualiserApp(luigi) {
                     });
                 }
                 else {
-                    window.location.href = 'index.html#tab=graph&visType=d3&taskId=' + taskId;
+                    fragmentQuery['taskId'] = taskId;
+                    window.location.href = 'index.html#' + URI.buildQuery(fragmentQuery);
                 }
             });
         }