Resolve "Redesign admin interface"
Introduce sidenav to admin interface which enables better overview, maintainability and expandability.
Also fix z-index of header toolbar and use variant colors of primary and secondary color according to material design.
Preview:
![](/-/project/14513497/uploads/bbd868ca8fc0275d564424bf77d8f066/localhost_4200_admin_stats_MDIP_.png)
Closes #834 (closed)