UI theming changes.

theme/style.less

@@ -1,2 +1,18 @@
 /* Import all components */
 @import 'semantic';
+@import 'themes/default/globals/site.variables';
+@import 'themes/pxt/globals/site.variables';
+@import 'site/globals/site.variables';
+
+/* Reference import */
+@import (reference) "semantic.less";
+
+/*******************************
+    Add your custom CSS here
+*******************************/
+
+.download-button {
+    &:extend(.ui all);
+    &:extend(.button all);
+    &:extend(.green all);
+}