Draft: RSD Plugin integration

Current implementation:

• in settings.json define plugin name in host:

{
  "host": {
    }, 
    # .....
    "modules":["software","projects","organisations"],
    "plugins": ["consult"]
  }
}

• next queries the backend server side via url /modules/<plugin>/config after the user logged in and sends the JWT token in header
• next expects a list of plugin slots with these properties:

export type PluginSlot={
  name: string,
  icon: JSX.Element,
  href: string,
  title: string,
  subtitle: string | null
}

• icon can e.g. be <svg>..</svg>
• currently there exists only one plugin slot name "userMenuItem" which will show up in the drop down user menu