Remove UTF8 BMP unit test and replace it with a general UTF8 test

Summary:
Ref T1191. After utf8mb4 conversion, these tests no longer pass because MySQL allows emoji and gclefs and such.

We could keep these tests running by keeping a `ut8f_bin` table around somewhere, but we have no other use cases for it and it does not seem worth the added complexity. All these BMP-only codepaths are on the way out.

Update the `%s` / `%B` test to make sure it's rejecting invalid byte sequences, which are still not permitted.

Test Plan: Tests now pass.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10621
Strip email signatures from Mailbox

Summary: thanks mailbox

Test Plan: unit tests

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D10629
Correct column mutations for old versions of MySQL

Summary:
Ref T1191. Although I fixed some of the mutations earlier (in D10598), I missed the column mutations under old versions of MySQL. In particular, this isn't valid:

  - `ALTER TABLE ... MODIFY columnName VARCHAR(64) COLLATE binary`

Issue the permitted version of this instead, which is:

  - `ALTER TABLE ... MODIFY columnName VARBINARY(64)`

Also fixed an issue where a clean schema had the wrong nullability for a column in the draft table. Force it to the expected nullability.

The other trick here is around the one column with a FULLTEXT index on it, which needs a little massaging.

Test Plan:
  - Forced my local install to return `false` for utf8mb4 support.
  - Did a clean adjust into `binary` columns.
  - Poked around, added emoji to things.
  - Reverted the fake check and did a clean adjust into `utf8mb4` columns.
  - Emoji survived.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: fabe, epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10627
Remove old, confusing configuration files

Summary:
Fixes T6230. These files have not been read by default for a long time, but users are frequently confused and try to edit `default.conf.php`.

Remove the actual files. Allow `phabricator_read_config_file(...)` to continue working as though they exist so as to not break config-file-based installs.

Test Plan:
I used this script to make sure that removing `default.conf.php` won't change things for installs which are still using config files:

```
<?php

require_once 'scripts/__init_script__.php';

$file = require 'conf/default.conf.php';
$global = new PhabricatorConfigDefaultSource();
$global_values = $global->getAllKeys();

foreach ($file as $key => $value) {
  $global_value = idx($global_values, $key, (object)array());

  if ($value !== $global_value) {
    echo "{$key}\n\n";
    echo "FILE VALUE\n";
    var_dump($value);
    echo "\n";
    echo "DEFAULT VALUE\n";
    var_dump($global_value);
    return;
  }
}
```

These were the keys that had issues:

  - `log.access.format` Not specified in default.conf.php, safe to speciy.
  - `mysql.pass` Empty string in file, null in global. Same effect.
  - `metamta.default-addrress` One used `noreply@example.com`, one `noreply@phabricator.example.com`. These are just human-readable examples so it's safe to change behavior.
  - `metamta.domain` same as above, `example.com` vs `phabricator.example.com`.
  - `phpmailer.smtp-host` One used null, one empty string.
  - `phpmailer.smtp-protocol` As above.
  - `files.viewable-mime-types` File version is out of date.
  - `repository.default-local-path` Null in file, set in global. This is correct to set to a default value now.
  - `pygments.dropdown-choices` File version is out of date.
  - `environment.append-paths` File version is empty, global version adds common paths. This //could// change behavior, but the web behavior is better and more reasonable in general, and a system would need to be configured in a very bizarre way for this to be relevant.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6230

Differential Revision: https://secure.phabricator.com/D10628
Add a setup warning about innodb_buffer_pool_size

Summary: Fixes T6119. This is a little fuzzy, but generally bumping up `innodb_buffer_pool_size` to something bigger than the default (which is often anemic, at `8M`) is desriable, and it seems like it will fix the specific issue a user encountered in T6119.

Test Plan: {F211855}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6119

Differential Revision: https://secure.phabricator.com/D10630
Implement storage of a host ID and a public key for authorizing Conduit between servers

Summary:
Ref T4209.  This creates storage for public keys against authorized hosts, such that servers can be authorized to make Conduit calls as the omnipotent user.

Servers are registered into this system by running the following command once:

```
bin/almanac register
```

NOTE: This doesn't implement authorization between servers, just the storage of public keys.

Placing this against Almanac seemed like the most sensible place, since I'm imagining in future that the `register` command will accept more information (like the hostname of the server so it can be found in the service directory).

Test Plan: Ran `bin/almanac register` and saw the host (and public key information) appear in the database.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T4209

Differential Revision: https://secure.phabricator.com/D10400
Create new databases with appropriate collation

Summary: Ref T1191. We don't create new databases with appropriate collation yet.

Test Plan:
Created a new database and saw it issue:

```
>>> [10] <query> CREATE DATABASE IF NOT EXISTS `phabricator2_testo` COLLATE utf8mb4_bin
```

Reviewers: btrahan, hach-que

Reviewed By: hach-que

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10632
Merge branch 'master' of github.com:facebook/phabricator