Add entry to select between normal and tweaked Link Force

- Tweaked link force should initialize and perform the calculation a tiny bit faster (maybe insignificant)

examples/js/src/neighbourSampling-papaparsing.js

@@ -42,7 +42,8 @@ var nodes, // as in Data points
   selectedData,
   clickedIndex = -1,
   paused = false,
-  alreadyRanIterations;
+  alreadyRanIterations,
+  tweakedVerOfLink;
 
 // Default parameters
 var MULTIPLIER = 50,

examples/js/src/neighbourSampling-papaparsing/linkForce.js

@@ -32,14 +32,15 @@ function startLinkSimulation() {
    * The full pre-calculation will then occur once when the force is being
    *   initialized by the simulation.
    */
-  simulation.force(forceName,
-    d3.forceLinkOptimized()
-      .distance(function (n) {
+  let force = tweakedVerOfLink ? d3.forceLinkTweaked() : d3.forceLink();
+  force.distance(function (n) {
          return distanceFunction(n.source, n.target, props, norm);
-       })
-    .links(links)
-  ).alphaDecay(0)
-    //.velocityDecay(0.8)
-   .alpha(1)
-   .restart();
+        })
+       .links(links);
+  
+  simulation.force(forceName,force)
+            .alphaDecay(0)
+             //.velocityDecay(0.8)
+            .alpha(1)
+            .restart();
 }