DS-2103: Reordering/Reorganizing of Administrative menu

https://jira.duraspace.org/browse/DS-2103

This PR reorders the Administrative menu in the XMLUI to this ordering:

ADMINISTRATIVE MENU

* Control Panel
* Access Control
  * People
  * Groups
  * Authorizations
* Content Administration (new grouping)
  * Items
  * Withdrawn Items
  * Private Items
  * Import Metadata
* Registries
  * Metadata
  * Format
* Administrative Statistics (renaming of "Statistics")
* Curation Tasks