Add z-index Sass map
Set dropdown z-index on main nav

Fixes z-index issue on tabbed pages
Remove calls to MOH site from main site header
Gentler CSS transitions on main-nav
Remove borders from nav-main

Also removes some box-shadow acting as border
Mimic li element bullets in nav-main
Fix bottom links in nav-main
Lighten nav-main bg
Lighter border in nav-main cols
Merge branch 'meganav-v2' into prod