Bootstrap FreeBSD server with Salt

Summary:
Install Salt and minimal software to run the states.

Git is installed too for servers not yet in the private network.

ASCII art credit: Jason Balthis

Ref T1803

Test Plan: Tested with db-B-001 and web-001

Reviewers: dereckson

Reviewed By: dereckson

Subscribers: fauve

Maniphest Tasks: T1803

Differential Revision: https://devcentral.nasqueron.org/D2978