Add an SSH access log

Summary: Ref T4107. Ref T4189. This implements an SSH access log, similar to the HTTP access log.

Test Plan:
  [Thu, 05 Dec 2013 13:45:41 -0800]	77841	orbital	::1	dweller	epriestley	epriestley	git-receive-pack	/diffusion/POEMS/	0	324765	402	232
  [Thu, 05 Dec 2013 13:45:48 -0800]	77860	orbital	::1	dweller	epriestley	epriestley	git-receive-pack	/diffusion/POEMS/	0	325634	402	232

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4107, T4189

Differential Revision: https://secure.phabricator.com/D7719
Fix an error in the PolicyFilter algorithm

Summary:
`PhabricatorPolicyFilter` has a bug right now where it lets through objects incorrectly if:

  - the query requests two or more policies;
  - the object satisfies at least one of those policies; and
  - policy exceptions are not enabled.

This would be bad, but there's only one call in the codebase which satisfies all of these conditions, in the Maniphest batch editor. And it's moot anyway because edit operations get another policy check slightly later. So there is no policy/security impact from this flaw.

(The next diff relies on this behavior, which is how I caught it.)

Test Plan:
  - Added a failing unit test and made it pass.
  - Grepped the codebase for `requireCapabilities()` and verified that there is no security impact. Basically, 99% of callsites use `executeOne()`, which throws anyway and moots the filtering.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7721