Introduce "bin/repository" for repository management

Summary:
Nothing new or exciting here yet, just moving the random scripts/repositories/ things to bin/repository. Also add repository list.

(Console stuff comes from D2841.)

Test Plan: Ran repository list, repository pull, repository discover, repository discover --verbose, repository help.

Reviewers: jungejason, vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D2849