Make content section expand at least to all available height.

services/web/public/stylesheets/core/scaffolding.less

@@ -33,6 +33,11 @@ body {
   position: relative;
   padding-top: @header-height;
   padding-bottom: @footer-height;
+  display: flex;
+  align-items: stretch;
+  > .content {
+    flex-grow: 1;
+  }
 }
 
 // Reset fonts for relevant elements