Don't raise a policy exception if a user can't see the parent revision of a new diff

Summary: Ref T603. We currently bomb out here, but should just continue forward. I'm fairly certain we don't even use this for anything anymore (it has been replaced by "depends on") but need to check that.

Test Plan: Created a new revision with `arc diff`.

Reviewers: ljalonen, btrahan, #blessed_reviewers, chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7255
Always pass handles to tokenizers, not `<phid -> name>` maps

Summary: Ref T1279. Prerequisite for adding icons or other type information to tokenizers, since we don't currently have enough information to prefill them when rendering things from the server side. By passing handles in, the tokenizer can extract type information.

Test Plan:
- Searched by user in Audit.
- Sent Conpherence from profile page.
- Tried to send an empty conpherence.
- Searched Countdown by user.
- Edited CCs in Differential.
- Edited reviewers in Differential.
- Edited a commit's projects.
- Searched lint by owner.
- Searched feed by owner/project.
- Searched files by owner.
- Searched Herald by owner.
- Searched Legalpad by owner.
- Searched Macro by owner.
- Filtered Maniphest reports by project.
- Edited CCs in Maniphest.
- Searched Owners by owner.
- Edited an Owners package.
- Searched Paste by owner.
- Searched activity logs by owner.
- Searched for mocks by owner.
- Edited a mock's CCs.
- Searched Ponder by owner.
- Searched projects by owner.
- Edited a Releeph project's pushers.
- Searched Releeph by requestor.
- Edited "Uses Symbols" for an Arcanist project.
- Edited all tokenizers in main search.
- Searched Slowvote by user.

Reviewers: chad, btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1279

Differential Revision: https://secure.phabricator.com/D7248
Remove dead `rejectImpossiblePolicy()` method

Summary: Ref T603. Apparently we made all policies possible at some point. Go us! This has no callsites.

Test Plan: `grep`, notice it's a private method

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7259
Allow applications to define new policy capabilities

Summary:
Ref T603. I want to let applications define new capabilities (like "can manage global rules" in Herald) and get full support for them, including reasonable error strings in the UI.

Currently, this is difficult for a couple of reasons. Partly this is just a code organization issue, which is easy to fix. The bigger thing is that we have a bunch of strings which depend on both the policy and capability, like: "You must be an administrator to view this object." "Administrator" is the policy, and "view" is the capability.

That means every new capability has to add a string for each policy, and every new policy (should we introduce any) needs to add a string for each capability. And we can't do any piecemeal "You must be a {$role} to {$action} this object" becuase it's impossible to translate.

Instead, make all the strings depend on //only// the policy, //only// the capability, or //only// the object type. This makes the dialogs read a little more strangely, but I think it's still pretty easy to understand, and it makes adding new stuff way way easier.

Also provide more context, and more useful exception messages.

Test Plan:
  - See screenshots.
  - Also triggered a policy exception and verified it was dramatically more useful than it used to be.

Reviewers: btrahan, chad

Reviewed By: btrahan

CC: chad, aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7260
Remove AphrontRedirectException

Summary: Fixes T3909. Waiting on Facebook to confirm this is unused.

Test Plan: `grep`

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T3909

Differential Revision: https://secure.phabricator.com/D7193
Adds status colors to navbar tabs

Summary: Adds the abilit to set a status color of warning or fail to navbar tab lists (for objectheaders)

Test Plan: uiexamples, photoshop

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7266