Pat Kira authored Mar 22, 2017 and Kristina Hoeppner committed Mar 22, 2017

- Added missing header bottom border (Default theme)
- Edited navbar colours and toggles (Default theme)
- Updated navbar-toggle colors and styles (Default theme)
- Updated main-nav.scss so any colour values set in 
  bootstrap-variables.scss is sane, the goal is to minimise having to 
  manually override navigation styles (Raw theme)

behatnotneeded: styling only

Change-Id: Idc82697d453be4a6dc1ad9169a1d36c17dab1b90