Add a "jump nav" element to the homepage, for quick tool/object navigation

Summary:

• Restore quick methods for getting to common features (upload file, create

task, etc.)

• Provide a flexible cli-like navigation element similar to stuff used at

Facebook (bunny1 / lolbunny).

Test Plan: Used jump nav and nav buttons.

Reviewers: btrahan, fratrik

Reviewed By: btrahan

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1619