Add side menu support + other core layout changes

-A new side menu option was added for displaying menu items vertically on the left-hand side of the page
-Added a new script called OverlayScrollbars v1.13.3 for displaying custom scrollbars on the mobile menu (both top and side menu) in the event that they extend beyond the visible screen
-Updated the market menu dropdown colors to better match the base menu colors (default, light and dark colors only)
-Updated the Exor theme to v3.0.1 with a few small fixes for displaying menu items in the side menu and updated market dropdown colors
-Updated how the richlist pie chart is sized to prevent it from creating unnecessary scrollbars because of the side menu
-Search field and button are now hidden in the top menu when the mobile menu is expanded to make it easier to scroll through menu items
-Added a tooltip title to the top menu search and menu toggler buttons

lib/settings.js

@@ -154,6 +154,10 @@ exports.shared_pages = {
   "show_hashrate": true,
   // page_header: A collection of settings that pertain to the page header that is displayed at the top of all pages
   "page_header": {
+    // menu: Valid options:
+    //       top: display menu items horizontally across the top of the page
+    //       side: display menu items vertically across the left-hand side of the page
+    "menu": "top",
     // sticky_header: Determine whether page header "sticks" to top of page or not (true/false)
     "sticky_header": true,
     // bgcolor: Change the background color of the page header