[Command] Added LockHelper

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes https://github.com/symfony/symfony/pull/10475
| Applies to    | Symfony version 2.6+
| Fixed tickets | -
This kind of makes it sound like this feature helps *only* in avoiding multiple people accessing
the same "computer file" - not something more generic. I'm ok with it really, but maybe you can
find some better wording.