Allow MQTT keep alive value of up to 3600s

code/html/index.html

@@ -597,7 +597,7 @@
 
                                 <div class="pure-g">
                                     <label class="pure-u-1 pure-u-lg-1-4">MQTT Keep Alive</label>
-                                    <input class="pure-u-1 pure-u-lg-1-4" type="number" name="mqttKeep" min="10" max="60" tabindex="28" />
+                                    <input class="pure-u-1 pure-u-lg-1-4" type="number" name="mqttKeep" min="10" max="3600" tabindex="28" />
                                 </div>
 
                                 <div class="pure-g module module-mqttssl">