Allow to generate RFC 4122 UUID v4

Summary:
Code by Andrew Moore
http://php.net/manual/en/function.uniqid.php#94959

Reference: https://www.ietf.org/rfc/rfc4122.txt

Imported from rKGF at 880c6bbe202d.

Test Plan: Units tests included

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1610