Allow multiple LDAP search filters, and complex search queries

Summary: Ref T3208. I'm going to make some people try this before it gets anywhere near landing.

Test Plan: oh man LDAP

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley, frgtn, aran

Maniphest Tasks: T3208

Differential Revision: https://secure.phabricator.com/D8159