Add admin menu and data management page

• Add a menu in BiscuIT-ng, labeled, Admin, only shown to superusers (for now)
• Add a view and template for a data management page and add this to the Admin menu
• On the data mangement page, render a completely new menu, called DATA_MANAGEMENT_MENU or whatever
• Have the Untis and SchILD-NRW apps add their menu items to the data management menu
• Remove the main menu links in these two apps

changed milestone to %1.0a0

added part::backend part::frontend prio::2 labels

marked the checklist item Remove the main menu links in these two apps as completed

marked the checklist item Have the Untis and SchILD-NRW apps add their menu items to the data management menu as completed

mentioned in commit c4cf0713

mentioned in merge request !38 (merged)

marked the checklist item On the data mangement page, render a completely new menu, called DATA_MANAGEMENT_MENU or whatever as completed

marked the checklist item Add a view and template for a data management page and add this to the Admin menu as completed

marked the checklist item Add a menu in BiscuIT-ng, labeled, Admin, only shown to superusers (for now) as completed

mentioned in commit a24fd548

mentioned in commit 911b21dd

mentioned in commit 1850c822

closed via merge request !38 (merged)

mentioned in commit cc73842f