R1:52c0ec270061

Update Phabricator logo

Summary:
This updates the eye logo and removes the formal wordmark "Phabricator" as an image. Instead we'll use the new updated eye logo and plain text for "Phabricator", both of which are more friendly and less industrial.

Installs that already use the `header-logo` customization setting will need to rebuild their logo to 80px x 80px. They will then also get to use plain text to whitebox their install as they see fit.

Test Plan:
Tested new logo at desktop, tablet, and mobile…