Ldap/Query: re-add __toString

We stopped using __toString as it is unable to handle exceptions - and
this makes sense. However, that's IMO not a good reason to completely
drop __toString. Especially when debugging, benchmarking and similar you
often need a quick way to "dump" an object.

In that case you are often not in a mood to figure out whether that
specific class prefers create(), dump(), render() or whatever. We should
not base our view scripts on __toString - at least unless we do not catch
Exceptions in __toString methods, eventually "forwarding" them as triggered
error where needed.

library/Icinga/Protocol/Ldap/Query.php

@@ -348,6 +348,11 @@ public function create()
         }
     }
 
+    public function __toString()
+    {
+        return $this->create();
+    }
+
     /**
      * Descructor
      */