Ch 561: Create a unified navigation to be integrated across menu modules.

The following directories are just straight additions from navbar:
* css/navbar
* css/icons
* css/images
* js/navbar
Each one has a README.md file to explain.

Both to avoid multiple setting of self but also because the updateUnifiedToolbarPosition can be called in different scopes and wanted to reference the getAdminMenu from it.  Incidentally, the getAdminMenu is included in both admin_menu and toolbar integration JS files.  I'm going to update them to be specific to their integration rather than having the more generic handler.