Remove standalone SMS support in favor of a "Mail, SMS, and other media are mostly the same thing" approach

Summary:
Ref T920. Over time, mail has become much more complex and I think considering "mail", "sms", "postcards", "whatsapp", etc., to be mostly-the-same is now a more promising avenue than building separate stacks for each one.

Throw away all the standalone SMS code, including the Twilio config options. I have a separate diff that adds Twilio as a mail adapter and functions correctly, but it needs some more work to bring upstream.

This permanently destroys the `sms` table, which no real reachable code ever wrote to. I'll call this out in the changelog.

Test Plan:
  - Grepped for `SMS` and `Twilio`.
  - Ran storage upgrade.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T920

Differential Revision: https://secure.phabricator.com/D19939

scripts/sms/manage_sms.php

@@ -1,21 +0,0 @@
-#!/usr/bin/env php
-<?php
-
-$root = dirname(dirname(dirname(__FILE__)));
-require_once $root.'/scripts/__init_script__.php';
-
-$args = new PhutilArgumentParser($argv);
-$args->setTagline(pht('manage SMS'));
-$args->setSynopsis(<<<EOSYNOPSIS
-**sms** __command__ [__options__]
-    Manage Phabricator SMS stuff.
-
-EOSYNOPSIS
-  );
-$args->parseStandardArguments();
-
-$workflows = id(new PhutilClassMapQuery())
-  ->setAncestorClass('PhabricatorSMSManagementWorkflow')
-  ->execute();
-$workflows[] = new PhutilHelpArgumentWorkflow();
-$args->parseWorkflows($workflows);