Check parameter type

Since the setParent and setPosition arguments expect an object we should check that that is what being provided. Rationale - As a noob user of the CMF components I wasn't sure I was supposed to be passing the parent object or path. When passing the path I would get odd errors such as:
```
PHP Warning:  spl_object_hash() expects parameter 1 to be object, string given in /home/gnat/Projects/photography/vendor/doctrine/phpcr-odm/lib/Doctrine/ODM/PHPCR/UnitOfWork.php on line 942
PHP Warning:  get_class() expects parameter 1 to be object, string given in /home/gnat/Projects/photography/vendor/doctrine/phpcr-odm/lib/Doctrine/ODM/PHPCR/UnitOfWork.php on line 944
```

This change fails sooner and in a better way in my opinion.

Author: gnat42

Doctrine/Phpcr/Route.php

@@ -14,6 +14,7 @@
 
 use Doctrine\Common\Collections\Collection;
 use Doctrine\ODM\PHPCR\Document\Generic;
+use Doctrine\ODM\PHPCR\Exception\InvalidArgumentException;
 use Symfony\Cmf\Component\Routing\RouteObjectInterface;
 use Symfony\Cmf\Bundle\RoutingBundle\Model\Route as RouteModel;
 
@@ -96,6 +97,9 @@ public function setAddTrailingSlash($addTrailingSlash)
      */
     public function setParent($parent)
     {
+        if(!is_object($parent))
+            throw new InvalidArgumentException("Parent must be an object ".gettype ($parent)." given.");
+
         $this->parent = $parent;
 
         return $this;
@@ -138,6 +142,9 @@ public function getName()
      */
     public function setPosition($parent, $name)
     {
+        if(!is_object($parent))
+            throw new InvalidArgumentException("Parent must be an object ".gettype ($parent)." given.");
+
         $this->parent = $parent;
         $this->name = $name;