Basic filename search support for Diffusion

Summary:
Ref T156. Adds basic filename search support for Diffusion,
currently only for Git repositories.

This is preliminary, and it's up for discussion:
  - is the UI in the right place;
  - what should the search query syntax be (e.g. whether
    to put `*`s in the beginning and end of it);
  - how to best approach it for Mercurial and/or SVN;
  - what's the cleanest result format for `lsquery` (I went
    for the minimum necessary change to `DiffusionBrowseSearchController`).

Test Plan:
Browse to a repository in Diffusion, and use both
`Search File Names` and `Search File Content`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T156

Differential Revision: https://secure.phabricator.com/D8093
Clean up the Diffusion search UI a little bit

Summary:
Ref T156. @vlada recently implemented filename search in Diffusion, this cleans up the UI a little bit:

  - Instead of showing one search box with two different buttons, let the submit buttons appear to the right of the text boxes and separate the search modes.
  - Clean up the results a little bit (don't show columns which don't exist).

Test Plan: {F107260}

Reviewers: vlada, btrahan, chad

Reviewed By: chad

CC: vlada, chad, aran

Maniphest Tasks: T156

Differential Revision: https://secure.phabricator.com/D8125
Remove retry/failure mechanisms from MetaMTA

Summary:
Fixes T4202. We have old code in MetaMTA which implements gradual backoff and maximum retries.

However, we have more general code in the task queue which does this, too. We can just use the more general stuff in the task queue; it obsoletes the specific stuff in MetaMTA, which is more complex and ran into some kind of issue in T4202.

Remove `retryCount`, `nextRetry` (obsoleted by task queue retry mechanisms) and "simulated failures" (no longer in use).

Generally, modern infrastructure has replaced these mechanisms with more general ones.

Test Plan:
  - Sent mail.
  - Observed unsendable mail failing in reasonable ways in the queue.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4202

Differential Revision: https://secure.phabricator.com/D8115
Expand aggregate email recipients prior to multiplexing

Summary:
Ref T4361. Before we figure out which To/CC are addressable, try to expand To/CC. Specifically, the supported expansion right now is project PHIDs expanding to all their members.

Because of the way multiplexing works, we have to do this in two places: explicitly in `multiplexMail()`, and when sending mail that wasn't multiplexed. This is messy; eventually we can get rid of it (after ApplicationTransactions are everywhere).

This has some rough edges, but should basically give us what we need to make stuff like projects mailable. Particularly, it deals with most issues in D7436:

  - I got around the resolution/multiplexing issue by resolving aggregate mailables separately from mailable actors.
  - We get to keep the Project PHID as a To/CC/Reviewer/Whatever until the last second.
  - Users won't get two emails for being a CC and also a member of a CC'd project.
  - We can degrade to the list stuff this way if we want, by having the project aggregate yield a single list PHID.

Test Plan: Added a comment to a revision with a project reviewer, got mail to all the project's members.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4361

Differential Revision: https://secure.phabricator.com/D8117
Fix the `What's New?` phabricatorbot handler.

Summary: `What's new` has been broken for awhile, I've updated it to use the `feed.query` text view.

Test Plan: Start up a bot and say "What's new?"

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: fas, epriestley, aran, Kage, demo

Differential Revision: https://secure.phabricator.com/D8118
Merge remote-tracking branch 'upstream/master' into release