Report on airtime-celery service in status

Adds celery checks to /?config and /systemstatus for completeness' sake.

Fixes #138

airtime_mvc/application/views/scripts/systemstatus/index.phtml

@@ -13,6 +13,7 @@
     $pypo =          $externalServices["pypo"];
     $liquidsoap =    $externalServices["liquidsoap"];
     $analyzer =      $externalServices["analyzer"];
+    $celery =        $externalServices['celery'];
 
     $r1 = array_reduce($phpDependencies, "booleanReduce", true);
     $r2 = array_reduce($externalServices, "booleanReduce", true);
@@ -149,6 +150,26 @@
                 ?>
             </td>
         </tr>
+        <tr>
+            <td class="component">
+                Celery
+            </td>
+            <td class="description">
+                LibreTime Celery Task service
+            </td>
+            <td class="solution <?php if ($celery) {echo 'check';?>" >
+                <?php
+                } else {
+                    ?>">
+                    Check that the airtime-celery service is installed correctly in <code>/etc/init</code>, 
+                    and ensure that it's running with
+                    <br/><code>initctl list | grep airtime-celery</code><br/>
+                    If not, try <br/><code>sudo service airtime-celery restart</code>
+                <?php
+                }
+                ?>
+            </td>
+        </tr>
     </tbody>
     <tr id="partitions" class="even">
         <th colspan="5"><?php echo _("Disk Space") ?></th>