Performance improvement when providing bundle id

This pull request is done to avoid as much as possible the use of exec() in Workflows constructor. When providing bundled when creating Workflows, I get good improvements.

I've created a workflow to show the improvements, get it here https://cloudup.com/cfurj0JsgsO

See:

![capture decran 2014-07-12 a 00 21 21](https://cloud.githubusercontent.com/assets/4061923/3559404/c885a6f0-0949-11e4-941f-8508162d53d6.png)