Feature: LDC-605 Add permission 'use Admin Theme'

## Ready State: Yes

Re-export the imagex_user_permissions module to ensure that the following roles use Admin Theme instead of the regular website theme. The roles are: Content Administrator, Content Creator, Content Manager and Content Moderator.

## Deployment Instructions

* Merge code.
* Go to Features ->User Permissions -> Revert
* Clear caches with `drush cache-clear all`

## Usage/Test Instructions

* Login user. The roles are: Content Administrator, Content Creator, Content Manager and Content Moderator.
* Add new content, edit etc