Exports - Improved exports time

- Use java DocumentBuilder to create XML document as groovy objects were consumming much more time
- Go through only one list when creating the exports: It's been noticed that the second list is only necessary when we use limits in the first query.
- Created the Export Service in order to separate most of the script from the Controller and improve code reuse.
- Removed exports from the current subscriptions and current Licences pages.