R1:7a3f33b5c293

OAuth - Phabricator OAuth server and Phabricator client for new Phabricator OAuth Server

Summary:
adds a Phabricator OAuth server, which has three big commands:
- auth - allows $user to authorize a given client or application. if $user has already authorized, it hands an authoization code back to $redirect_uri
- token - given a valid authorization code, this command returns an authorization token
- whoami - Conduit.whoami, all nice and purdy relative to the oauth server.
Also has a "test" handler…