Move subtask forecast to a plugin

Plugin repo: https://github.com/kanboard/plugin-subtask-forecast

tests/units/Helper/HookHelperTest.php

@@ -0,0 +1,40 @@
+<?php
+
+require_once __DIR__.'/../Base.php';
+
+use Helper\Hook;
+
+class HookHelperTest extends Base
+{
+    public function testMultipleHooks()
+    {
+        $this->container['template'] = $this
+            ->getMockBuilder('\Core\Template')
+            ->setConstructorArgs(array($this->container))
+            ->setMethods(array('render'))
+            ->getMock();
+
+        $this->container['template']
+            ->expects($this->at(0))
+            ->method('render')
+            ->with(
+                $this->equalTo('tpl1'),
+                $this->equalTo(array())
+            )
+            ->will($this->returnValue('tpl1_content'));
+
+        $this->container['template']
+            ->expects($this->at(1))
+            ->method('render')
+            ->with(
+                $this->equalTo('tpl2'),
+                $this->equalTo(array())
+            )
+            ->will($this->returnValue('tpl2_content'));
+
+        $h = new Hook($this->container);
+        $h->attach('test', 'tpl1');
+        $h->attach('test', 'tpl2');
+        $this->assertEquals('tpl1_contenttpl2_content', $h->render('test'));
+    }
+}