Expose SubTask Time Tracking though the API

Also allow users to create Subtasks and Log Time for Subtasks through the User API

Rebased to new API code

app/Api/SubtaskTimeTracking.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Kanboard\Api;
+
+/**
+ * Subtask Time Tracking  API controller
+ *
+ * @package  api
+ * @author   Nikolaos Georgakis
+ */
+class SubtaskTimeTracking extends \Kanboard\Core\Base
+{
+    public function hasTimer($subtask_id,$user_id)
+    {
+        return $this->subtaskTimeTracking->hasTimer($subtask_id,$user_id);
+    }
+
+    public function logStartTime($subtask_id,$user_id)
+    {
+        return $this->subtaskTimeTracking->logStartTime($subtask_id,$user_id);
+    }
+
+    public function logEndTime($subtask_id,$user_id)
+    {
+        return $this->subtaskTimeTracking->logEndTime($subtask_id,$user_id);
+    }
+
+    public function getTimeSpent($subtask_id,$user_id)
+    {
+        return $this->subtaskTimeTracking->getTimeSpent($subtask_id,$user_id);
+    }
+}