* Add "archweb.css" from the master branch of archweb. We will use this
  as base style sheet in the future.

* Add "aur.css" for AUR-specific extensions to "archweb.css".

* Remove the "archnavbar.css" link from the header template since this
  is included in "archweb.css".

Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>