Move .less files to dev/less

dev/less/util.less

@@ -0,0 +1,24 @@
+.dark {
+    color: @black !important;
+}
+
+.light {
+    color: @gray !important;
+}
+
+.accent {
+    color: @accent !important;
+}
+
+.small-screens-only {
+    @media (min-width: 550px) {
+        display: none;
+    }
+}
+
+.large-screens-only {
+    display: none;
+    @media (min-width: 550px) {
+        display: initial;
+    }
+}