Often, folks run into two issues when they create new menus: they click "Add a Menu" thinking it will add a new page to their menu, or they forget to assign their new menu to a location, and then wonder why it doesn't show up on their site.
This commit rearranges the order of items in the menu panel, and updates the flow for creating a menu by breaking it up into steps. Additionally, more help text has been added to guide people through the process of creating a menu.
Also adds default `type` lookups for Panel and Section instances. See #30741.
Props bpayton, obenland, westonruter, celloexpessions, afercia, melchoyce, zoonini, michelleweber.
Fixes#40104.
Built from https://develop.svn.wordpress.org/trunk@41768
git-svn-id: http://core.svn.wordpress.org/trunk@41602 1a063a9b-81f0-0310-95a4-ce76da25c4cd
