This is the main header. If the megamenu doesn't have a feature with it - the `.header-nav-feature` element MUST remain in place, just left empty.
Column management is handled by Umbraco and classes added depending on the number of columns a nav should take up:
Within header-nav-menu-items the direct descendents should be nav elements with one of the following classes:
header-nav-menu-items--singleheader-nav-menu-items--doubleheader-nav-menu-items--trebleheader-nav-menu-items--quadruple