Put a Phage skeleton command on the Arcanist experimental branch
Summary:
Ref T2794. This doesn't do anything useful, but since I'm planning to start using this stuff to do real deployments I don't want to lose it if my laptop gets hit by a bus.
This just adds a skeletal bin/phage with enough code that I can add actual workflows to Phacility repositories and get bin/phage remote --hosts ... working without the code only existing on my laptop.
Test Plan: Ran bin/phage, saw nothin'.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T2794
Differential Revision: https://secure.phabricator.com/D17379