Varnish bypass at user level

Hi,

For purposes of testings, I needed to develop one additional functionality. And I think it might be useful for others users.

This feature allows you to bypass Varnish at the user session level. With this new granularity, we can navigate without Varnish and without disabling Varnish globally for all your users.
**This feature simply uses a cookie and the verification is done inside the VCL files.**

I've added a new button in "Cache Management". So, you can add/remove the bypass cookie here. I have attached some screenshots below:
+ *When you don't have the bypass cookie (Cache Management)*
![bypass - off](https://f.cloud.github.com/assets/3305232/578560/80d9c2d0-c85b-11e2-96e9-c75473931608.png)

+ *When you have the bypass cookie (Cache Management)*
![bypass - on](https://f.cloud.github.com/assets/3305232/578563/87ea5b70-c85b-11e2-932c-5bba25310078.png)

+ *When you have the bypass cookie (Front-office)*
![notice](https://f.cloud.github.com/assets/3305232/578564/899713b4-c85b-11e2-97b2-3781f10e0ace.png)

Let me know if you have any questions.