Moved current Router files to API

- updated Unit tests to reflect the change

tests/unit/API/SettingsTest.php

@@ -0,0 +1,51 @@
+<?php
+use \MailPoet\API
+    \Settings;
+use \MailPoet\Models\Setting;
+
+class SettingsTest extends MailPoetTest {
+  function _before() {
+    Setting::setValue('some.setting.key', true);
+  }
+
+  function testItCanGetSettings() {
+    $router = new Settings();
+
+    $settings = $router->get();
+    expect($settings)->notEmpty();
+    expect($settings['some']['setting']['key'])->true();
+
+    Setting::deleteMany();
+    $settings = $router->get();
+    expect($settings)->equals(Setting::getDefaults());
+  }
+
+  function testItCanSetSettings() {
+    $new_settings = array(
+      'some' => array(
+        'setting' => array(
+          'new_key' => true
+        ),
+        'new_setting' => true
+      )
+    );
+
+    $router = new Settings();
+
+    $response = $router->set(/* missing data */);
+    expect($response)->false();
+
+    $response = $router->set($new_settings);
+    expect($response)->true();
+
+    $settings = $router->get();
+
+    expect($settings['some']['setting'])->hasntKey('key');
+    expect($settings['some']['setting']['new_key'])->true();
+    expect($settings['some']['new_setting'])->true();
+  }
+
+  function _after() {
+    ORM::forTable(Setting::$_table)->deleteMany();
+  }
+}