Fix XML ACL to allow Roles to add the Zendesk Menu to Non Full Access Us...

I discovered that the Role Resources was missing the ability to Give the Zendesk Dropdown menu to a user who doesn't have full access. So I fixed the ACL.

It adds the following to the Role Resources Selector:

![administrators___roles___permissions___system___magento_admin](https://f.cloud.github.com/assets/20999/1351318/7e1d801a-3721-11e3-897a-b2b8de8f4670.png)