UI changes to match the calliope design.

theme/site/collections/menu.variables

@@ -1,3 +1,13 @@
 /*******************************
     User Variable Overrides
 *******************************/
+
+@invertedBackground: #525A67;
+@dropdownMenuDistance: 0px;
+
+/*******************************
+    PXT Theme Overrides
+*******************************/
+
+@mainMenuHeight: 5rem;
+@mainMenuMinHeight: (@itemVerticalPadding * 2) + 2em;