#445830: Follow-up to Rename clear-block CSS class to clearfix because I missed a few clear-block classes

Removed #sidebar-first, #sidebar-first-inner, #sidebar-second, #sidebar-second-inner and moved styles to .region-sidebar-first, .region-sidebar-first .section, .region-sidebar-second, .region-sidebar-second .section.

Renamed #navbar div to #navigation, $navbar region to $navigation, .with-navbar class to .with-navigation and added #navigation .section div