Only show top-level items when adding pages to a User's First Nav Menu. (This is also the title of Dave's first children's book.)

props lessbloat.
fixes #25122.


git-svn-id: https://develop.svn.wordpress.org/trunk@25622 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fourteen: change the background color a bit more on hover for main navigation submenus. See #25220.

git-svn-id: https://develop.svn.wordpress.org/trunk@25623 602fd350-edb4-49c9-b593-d223f7449a82