Store primes in sessionStorage to make reloading the page quicker.

templates/index.html

@@ -23,6 +23,10 @@
         <strong>Players</strong>
         <ul id="playerList">
         </ul>
+        <button id="shuffleColors">Shuffle colours</button>
+    </div>
+
+    <div id="remaining-reinforcements">
     </div>
 
     <div id="info">