ui: Let the bootstrap inverse navbar style shine through

ui: Let the bootstrap inverse navbar style shine through

Time for another iteration of the design. Let's start by using the
inverse bootsrap style with a slightly whiter color for font for better
contrast.

That color change has repercussions in the style sheet, mostly in the
custom containers/boxes we're still using on the secondary pages
(login/register/...)

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Stephen Finucane <stephen.finucane@intel.com>