Adding Rest Api Service Support

Rest Service on plugins
-----------------------

1. enable service

add the following line in plugin __constructor main class
$this->enableRestService(true);

2. Create the sources directory structure by example:
if you plugin is named myPlugin

myPlugin
    |--src
        |--Services
             |--Api
                 |--MyPlugin
                      |--Test.php

Where Test.php is a Restler class

workflow/engine/src/Services/Api/ProcessMaker/Test.php

@@ -1,7 +1,7 @@
 <?php
 namespace Services\Api\ProcessMaker;
 
-use \ProcessMaker\Api;
+use \ProcessMaker\Services\Api;
 use \Luracast\Restler\RestException;
 
 class Test extends Api