Adding Schema Support To Phinx

Looks like phinx just creates/looks for objects in default schema

example: SQL Server Create table will create table in dbo schema. Mysql will create table in database (database same as schema for mysql) that is set in connection property.

`<?php

use Phinx\Migration\AbstractMigration;

class MyNewMigration extends AbstractMigration
{
public function change()
{
$users = $this->table('users', '<schema_name>');
$users->addColumn('username', 'string', ['limit' => 20])
->addColumn('password', 'string', ['limit' => 40])
->addColumn('password_salt', 'string', ['limit' => 40])
->addColumn('email', 'string', ['limit' => 100])
->addColumn('first_name', 'string', ['limit' => 30])
->addColumn('last_name', 'string', ['limit' => 30])
->addColumn('created', 'datetime')
->addColumn('updated', 'datetime', ['null' => true])
->addIndex(['username', 'email'], ['unique' => true])
->create();
}
}`

Start from the AbstractMigration::table() call shown in the issue and trace how its table name is handled. Done means a migration can target a named schema, while existing default-schema behavior remains supported for SQL Server and MySQL.