R1:6f5dab634db2

Redesign header menus and search

Summary:
Still lots to fix here, punting up since I'm running into a few roadblocks.

TODO:
[] Sort Personal/Global correctly
[] Quicksand in Help Items correctly on page changes

Test Plan: Verify new menus work on desktop, tablet, mobile. Test logged in menus, logged out menus. Logging out via a menu, verify each link works as expected. Help menus get build when using an app like Maniphest, Differential. Check that search works, preferences still save.

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