Add SVG icons and empty howto page

templates/default-page.pug

@@ -6,16 +6,26 @@ block body
       .branding
         if noLogo
           .branding__backlink
-            a.icon-link.icon-link--primary(href='/') AOE Technology Radar
+            a.icon-link.icon-link--primary.icon-link--big(href='/')
+              span.icon.icon--back.icon-link__icon
+              | AOE Technology Radar
         if !noLogo
           a.branding__logo(href='/')
             img(src='/assets/logo.svg')
         .branding__content
           .nav
             .nav__item
-              a.icon-link(href='/howto.html') How to Use Technology Radar?
+              a.icon-link(href='/howto.html')
+                span.icon.icon--question.icon-link__icon
+                | How to Use Technology Radar?
             .nav__item
-              a.icon-link(href='/overview.html') Technologies Overview
+              a.icon-link(href='/overview.html')
+                span.icon.icon--overview.icon-link__icon
+                | Technologies Overview
+            .nav__item
+              a.icon-link(href='#todo')
+                span.icon.icon--search.icon-link__icon
+                | Search
     .page__content
       block content
     if !noFooter