feat(navigation): hard-switch to Zibll navigation and Font Awesome 5

assets/css/core/buttons.css

@@ -180,9 +180,6 @@
 
 .but .icon,
 .but > .fa:not(.fa-angle-right),
-.but > .fas:not(.fa-angle-right),
-.but > .far:not(.fa-angle-right),
-.but > .fab:not(.fa-angle-right),
 .but > i[class*="fa-"]:not(.fa-angle-right) { margin-right: 0.25em; }
 
 /* hover / active */