Graylog WUI customization

//Feature request
Make changeable some information/things on Graylog WUI, to be different from other graylog installations.
To be able to make difference between the playground and live system, foo and bar sites.
Also make the end user's life easier (hide unused menus, show useful info)
(Just some ideas)

Eg.:
- changeable login screen
-background
-corporate logo
-welcome message
-some useful info, eg. "you need your active directory logon without domain name"

- changeable navigation bar
-corporate logo
-highlight custom message (eg. LIVE system in foo)
-hide system menu, where not needed for users
-hide throughput
-background color of navbar (eg. red - dev; blue - live system)

- themes (change full site's coloring)