R1:226cf288e97c

Add active-directory domain-based ldap authentication support

Summary: Add active-directory domain-based ldap authentication support

Test Plan: Tested on a live install against Active Directory on a Windows Server

Reviewers: epriestley

CC: aran, epriestley

Maniphest Tasks: T1496

Differential Revision: https://secure.phabricator.com/D2966