Add arcanist and libphutil versions to /config/all/

Summary: Fixes T3453. Makes it easier for me to get version info when supporting users, since they can copy/paste from the web UI instead of running a bunch of `git` commands.

Test Plan: {F50749}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T3453

Differential Revision: https://secure.phabricator.com/D6491