Improve user feedback on the Profile > Design page

- Header changes immediately without a page reload
- Lets the user know that we actually saved their setting when changed

app/views/profile/update.js.erb

@@ -0,0 +1,9 @@
+// Remove body class for any previous theme, re-add current one
+$('body').removeClass('ui_basic ui_mars ui_modern ui_gray ui_color')
+$('body').addClass('<%= app_theme %>')
+
+// Re-render the header to reflect the new theme
+$('header').html('<%= escape_javascript(render("layouts/head_panel", title: "Profile")) %>')
+
+// Re-initialize header tooltips
+$('.has_bottom_tooltip').tooltip({placement: 'bottom'})