cubicweb-bootstrap #3595291 Clean and bootrapize the nav bar [validation pending]

The actuel nav bar is not fully bootrapized.

prioritynormal
typebug
done in0.5.0
load0.500
load left0.000
closed by<not specified>
patch[navbar] reduce the navbar size (related to #3595291) [applied][navbar] add a new class `cw-site-title` for the site title (related to #3595291) [applied][navbar] bootstrapize AuthenticatedUserStatus component (related to #3595291) [applied]