Provide an attached-to-visible-object policy exception for files

Summary:
Ref T603. This uses the existing edges (from Conpherence) to record that a file is attached to an object, and uses those edges to create a policy exception: if you can view an attached object, you can view a file.

I'm going to combine this with restrictive defaults to satisfy the other half of the equation (that files you attach to a conpherence usually shouldn't be public by default).

Test Plan:
  - Loaded `/files/`.
  - Uploaded a file to a Conpherence, looked at it in Files, saw the attachment.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7182
Add `viewPolicy` and `attachedToObjectPHID` to PhabricatorFile

Summary:
Ref T603. Principally, I want to implement the rule "when you upload a file to an object, users must be able to see the object in order to see the file", since I think this is strongly in line with user expectation. For example, if you attach a file to a Conpherence, it should only be visible to members of that thread.

This adds storage for policies, but doesn't do anything interesting with it yet.

Test Plan: Ran `bin/storage upgrade`.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7175
Fix an issue where email is overquoted when attaching objects

Summary:
Currently, if you attach a revision to a task and the revision has a title with quotes or angle brackets in it, they are over-escaped in the email.

Instead, don't do that.

Test Plan: Attached `"QUOTES" MATH: 1 < 2` to a task, got a reasonable looking email.

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D7186
Treat invalid policies as broadly similar to "no one"

Summary:
Ref T3903. Ref T603. We currently overreact to invalid policies. Instead:

  - For non-omnipotent users, just reject the viewer.
  - For omnipotent users, we already shortcircuit and permit the viewer.
  - Formalize and add test coverage for these behaviors.

Also clean up some strings.

The practical effect of this is that setting an object to an invalid policy (either intentionally or accidentally) doesn't break callers who are querying it.

Test Plan:
  - Created a Legalpad document and set view policy to "asldkfnaslkdfna".
  - Verified this policy behaved as though it were "no one".
  - Added, executed unit tests.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603, T3903

Differential Revision: https://secure.phabricator.com/D7185
Fix a variable name PolicyFilter.
Maniphest "attach" actions should always have workflow
Update Phrequent to use new search infrastructure.

Summary:
This updates Phrequent to use new the search infrastructure.  Now it looks like:

{F60141}

I've also added the policy infrastructure stubs, but it's probably not even close to being right in terms of enforcing policies (in particular being able to see time tracked against objects the user wouldn't normally be able to see).

At some point I'd like to be able to filter on the objects that the time is tracked against, but I don't believe there's a tokenizer / readahead control that allows you to type any kind of object.

Test Plan: Clicked around the new interface, created some custom queries and saved them.

Reviewers: epriestley

CC: Korvin, aran

Maniphest Tasks: T3870

Differential Revision: https://secure.phabricator.com/D7163
Add "Stop Tracking" link to entries in the Phrequent search view.

Summary: Depends on D7163.  This adds a "Stop Tracking" link to the right-hand side of ongoing entries in the Phrequent search view.  It allows users to stop tracking items without first navigating to the item itself.

Test Plan: Started tracking and item and then clicked the "Stop Tracking" link in Phrequent.

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, aran

Maniphest Tasks: T3870

Differential Revision: https://secure.phabricator.com/D7164
ObjectBoxes for Diffusion

Summary: Two missed Object Box cases in Diffusion.

Test Plan: View an individual file in Diffusion

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: Korvin, aran

Differential Revision: https://secure.phabricator.com/D7187
Flags - add ability to group by color

Summary:
I use color to convey meaning like "good resource to keep handy for a bit on new way of doing things" or "snipe this task". Now the list can be grouped by these colors.

Note I do this in PHP 'cuz color isn't part of any index AFAIK and pragmatically speaking this dataset should be tiny in the context of "user flags".

Ref T1809

Test Plan: selected group by color and observed the flags were indeed grouped by color

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, aran

Maniphest Tasks: T1809

Differential Revision: https://secure.phabricator.com/D7188