Ability to "Create X" from wide sidebar buttons

Summary: Shorten home to 240, 3 items wide, add create button for certain wide apps.

Test Plan: Test in FF, Chrome, IE8/9

Reviewers: epriestley, btrahan, codeblock

Reviewed By: epriestley

CC: aran, Korvin, vrana

Differential Revision: https://secure.phabricator.com/D4555
Fix FileTreeView sprites

Summary: D4453 and D4427 sailed past one another, like ships in the night.

Test Plan: Verified Differential hover and selected states.

Reviewers: asherkin, chad

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D4577
Use white "+" icon for homepage tile hoverstate

Summary: The easiest approach here is proably to provide a more specific rule in the sheet CSS. This saves us from having to write any JS, notably.

Test Plan: Hovered over "+" on homepage.

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D4579