Added internal task links to activity stream

app/Template/notification/task_internal_link_create_update.php

@@ -0,0 +1,11 @@
+<h2><?= $this->text->e($task['title']) ?> (#<?= $task['id'] ?>)</h2>
+
+<p>
+    <?= e(
+        'This task is now linked to the task %s with the relation "%s"',
+        $this->url->link(t('#%d', $task_link['opposite_task_id']), 'TaskViewController', 'show', array('task_id' => $task_link['opposite_task_id'])),
+        $this->text->e($task_link['label'])
+    ) ?>
+</p>
+
+<?= $this->render('notification/footer', array('task' => $task, 'application_url' => $application_url)) ?>