Refs #2440: responsive header (HTML and CSS)
Refs #2440: custom background-color for hamburger menu
Refs #2440: avoid admin Drupal menu to overlap the header
Refs #2440: fixes for Migration slideshow on 800px
rounded corners for homepage calendar current date
remove border-bottom for About section on common portal homepage
margin-top for header only when logged in (Drupal admin menu visible)
Refs #2440: responsive header for secondary pages too