Add possibility to define namespace of Symfony Console Command

[o5]

With this change you can easily set your own command namespace in NEON (commandNamespace), YAML (command_namespace). It's needful when you have more databases.

NEON

migrations:
    dir: %appDir%/../migrations # migrations base directory
    driver: pgsql
    dbal: nextras
    commandNamespace: migrations:database1

OUTPUT

$ bin/console
migrations
  migrations:database1:continue             Updates database schema by running all new migrations
  migrations:database1:create               Creates new migration file with proper name (e.g. 2015-03-14-130836-label.sql)
  migrations:database1:reset                Drops current database and recreates it from scratch

REF: #94 (comment)

[mabar]

Default name should not be removed, even if not used in configure() because it breaks lazy loading.

Also commands with custom name can support lazy loading. In case of contributte/console could be added service tag $service->addTag('console.command', 'custom:command:name'). Not sure about kdyby/console and symfony DI integrations.

[o5]

Actually I wanted to not remove this static property but symfony-bundle test failed on a weird notice like "undefined index continue" in Symfony/Application.php.

I didn't know this is symfony "build-in feature" from v3.4.10 and I have the same opinion like https://twitter.com/Majkl578/status/1214523751603286016

Any ideas how to resolve it? I agree that breaking lazy loading is not good.

[mabar]

Sorry, bit forgot about that. Change of command name is supported directly by symfony/console CommandLoader. The actual implementation is DIC-specific, so usage depends on which integration you use. For symfony/dependency-injection it should be $service->tag('console.command', ['command' => 'namespaced:migrations:reset']). For others it should be quite similar.

So any change of nextras/migrations code should not be needed.