PM Rest Feature: added plugins support & more improvements

from a plugin a rest class can be registered now:

on setup method add the following:
---
$this->registerRestService('Sample', [optional string: $path]);
--

and create the folder   PATH_PLUGIN . /your_plugin/classes/rest

next add a class with the flowing characteristics:

<?php

class Plugin_Services_Rest_Sample
{
    public function get()
    {
        return 'hello world';
    }
}

A class prefixed with Plugin_Services_Rest_
and add the corresponding methods for a Restler api
(http://luracast.com/products/restler/)

Finally on process maker will be exposed as:

via GET: http://127.0.0.1/rest/workflow/sample

workflow/engine/classes/class.plugin.php

@@ -327,6 +327,34 @@ class PMPlugin
         $oPluginRegistry =& PMPluginRegistry::getSingleton();
         return $oPluginRegistry->getSteps();
     }
+
+    /**
+     * Register a rest service and expose it
+     *
+     * @author  Erik Amaru Ortiz <erik@colosa.com>
+     * @param string $coreJsFile
+     * @param array/string $pluginJsFile
+     * @return void
+     */
+    function registerRestService($classname, $path = '')
+    {
+        $oPluginRegistry =& PMPluginRegistry::getSingleton();
+        $oPluginRegistry->registerRestService($this->sNamespace, $classname, $path);
+    }
+
+    /**
+     * Unregister a rest service
+     *
+     * @author  Erik Amaru Ortiz <erik@colosa.com>
+     * @param string $coreJsFile
+     * @param array/string $pluginJsFile
+     * @return void
+     */
+    function unregisterRestService($classname, $path)
+    {
+        $oPluginRegistry =& PMPluginRegistry::getSingleton();
+        $oPluginRegistry->unregisterRestService($this->sNamespace, $classname, $path);
+    }
 }
 
 class menuDetail