Introduce drawer main menu

Preparation/Cleanup: Simplify navigation drawer component and service

Since we introduce a global modal drawer and we won't use another one, NavigationDrawerComponent and DrawerService can be simplified.

Drawer main menu

Create a overlay drawer for hosting main menu items of different kind:

• Information: Authentication status
• In-App-Navigation: Account settings, rooms, templates (only if has authentication)
• UI-Settings: Language selection, theme selection
• External/Special links: Administration, help, accessibility, data protection, imprint
• Authentication actions: Login/Logout depending on auth status

Since external links are always displayed in main menu no matter which route, device type or authentication status, they don't need to be displayed in the footer if a user is logged in (at least as guest).

Add tests for new main menu and stories for new/adjusted components.

Closes #1234 (closed)