Adds one entry point for both JSON and MP APIs

Removes endpoints folder and moves versions to the root
JSON API folder

tests/unit/API/JSON/v1/MailerTest.php

@@ -0,0 +1,21 @@
+<?php
+
+use MailPoet\API\JSON\v1\Mailer;
+use MailPoet\API\JSON\Response as APIResponse;
+use MailPoet\Mailer\MailerLog;
+
+class MailerEndpointTest extends MailPoetTest {
+  function testItResumesSending() {
+    // create mailer log with a "paused" status
+    $mailer_log = array('status' => MailerLog::STATUS_PAUSED);
+    MailerLog::updateMailerLog($mailer_log);
+    $mailer_log = MailerLog::getMailerLog();
+    expect($mailer_log['status'])->equals(MailerLog::STATUS_PAUSED);
+    // resumeSending() method should clear the mailer log's status
+    $mailer_endpoint = new Mailer();
+    $response = $mailer_endpoint->resumeSending();
+    expect($response->status)->equals(APIResponse::STATUS_OK);
+    $mailer_log = MailerLog::getMailerLog();
+    expect($mailer_log['status'])->null();
+  }
+}