cleanup reboot logic, fix json upload

rust/src_webpack/src/main.html

@@ -116,6 +116,9 @@
   <br>
   <textarea id="json" cols=50 rows=10></textarea>
   <script src="bundle.js"></script>
+
+  <button id="exit">Exit</button>
+  <button id="reboot">Reboot</button>
 </div>
 
 <div id="progressPane" class="progressPane">