isolateserver: add checkbox to enable ts_mon

appengine/isolate/templates/restricted_config.html

 {% set title = 'Isolate global config' %}
 {% extends "isolate/base.html" %}
 
+{% block headers %}
+<script>
+function onclick_ts_mon() {
+  document.getElementById("enable_ts_monitoring_hidden").disabled =
+    document.getElementById("enable_ts_monitoring").checked;
+  }
+</script>
+{% endblock %}
+
 {% block body %}
 <h1>Server global config</h1>
 
 Last updated by:
 <strong>{% if cfg.updated_by %}{{cfg.updated_by.to_bytes()}}{% else%}N/A{%endif%}
   </strong>.<br>
 Last updated on: <strong>{{cfg.updated_ts|datetimeformat}}</strong>.<br>
 
 {% if note %}
 <span style="color: red; font-style: italic">{{note}}</span><p>
 {% endif %}
 
 <form method="post" action="{{path}}">
   <h2>General</h2>
   Google Analytics ID:
   <input name="google_analytics" value="{{cfg.google_analytics}}"/><br>
 
   <h2>Cache</h2>
   <div>
     Default expiration (secs):<br />
     <input type="text" name="default_expiration"
         value="{{cfg.default_expiration}}" size="60" />
   </div>
+  <h2>Timeseries Monitoring</h2>
+  <div>
+   Enable: <input id="enable_ts_monitoring" type="checkbox" name="enable_ts_monitoring" value="True" onclick="onclick_ts_mon()" {% if cfg.enable_ts_monitoring %}checked{% endif %}>
+   <input id="enable_ts_monitoring_hidden" type="hidden" name="enable_ts_monitoring" value="False">
+  </div>
   <h2>Google storage</h2>
   See this <a href="https://developers.google.com/storage/docs/accesscontrol#About-the-Client-ID">
   page</a> for instructions on how to setup Service account for API Access to
   Google Storage.
   <p>
   <div>
     Google Storage Bucket:<br />
     <input type="text" name="gs_bucket" value="{{cfg.gs_bucket}}" size="60" />
   </div>
   <br>
@@ skipping 25 matching lines @@
   # Convert *.pem into *.der.
   openssl rsa -in secret.pem -inform PEM -out secret.der -outform DER
   # Base64 encode *.der and copy-paste it into the form above.
   cat secret.der | base64
   # Remove temp files.
   rm secret.der secret.pem
 </pre>
 </p>
 
 {% endblock %}