Add timer for subtasks and remove settings for subtask time tracking

app/Helper/Datetime.php

@@ -10,6 +10,39 @@ namespace Helper;
  */
 class Datetime extends \Core\Base
 {
+    /**
+     * Get the age of an item in quasi human readable format.
+     * It's in this format: <1h , NNh, NNd
+     *
+     * @access public
+     * @param  integer    $timestamp    Unix timestamp of the artifact for which age will be calculated
+     * @param  integer    $now          Compare with this timestamp (Default value is the current unix timestamp)
+     * @return string
+     */
+    public function age($timestamp, $now = null)
+    {
+        if ($now === null) {
+            $now = time();
+        }
+
+        $diff = $now - $timestamp;
+
+        if ($diff < 900) {
+            return t('<15m');
+        }
+        if ($diff < 1200) {
+            return t('<30m');
+        }
+        else if ($diff < 3600) {
+            return t('<1h');
+        }
+        else if ($diff < 86400) {
+            return '~'.t('%dh', $diff / 3600);
+        }
+
+        return t('%dd', ($now - $timestamp) / 86400);
+    }
+
     /**
      * Get all hours for day
      *