index.html: a new joyful clustering experience, reword 'cluster' menu

Closes #2335.

browser/index.html

@@ -140,14 +140,18 @@
 
                 <div class="menu" id="cluster_menu" onmouseover="showSelector('clusterSelector');" > cluster
                     <div id="clusterSelector" class="selector"><div>
-                        <a class="buttonSelector" onclick="m.restoreClusters();">clones merged by user</a>
-                        <a class="buttonSelector" onclick="m.resetClusters();">reset all user clones</a>
+                        <div class="menu_box">
+                          <a class="buttonSelector" onclick="m.restoreClusters();">revert to previous clusters</a>
+                        </div>
+                        <div class="menu_box">
                         <a class="buttonSelector" onclick="m.clusterBy(function(id){return m.clone(id).getGene(5)});">cluster by V/5' </a>
                         <a class="buttonSelector" onclick="m.clusterBy(function(id){return m.clone(id).getGene(3)});">cluster by J/3' </a>
                         <a class="buttonSelector" onclick="m.clusterBy(function(id){return m.clone(id).germline});">cluster by locus </a>
                         <a class="buttonSelector devel-mode" onclick="m.similarity_builder.DBscan(95,0.001);">cluster by DBscan (experimental) </a>
                         <a class="buttonSelector" onclick="m.similarity_builder.cluster_me(95,0.1);">cluster by similarity </a>
                         <div id="clusterby_button"> </div>
+                        <a class="buttonSelector" onclick="m.resetClusters();">reset all clusters</a>
+                        </div>
                     </div></div>
                 </div>