[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 | -
What about explaining a bit more the purpose of the first argument?

```
The first argument of the ``LockHandler`` is a string that it will be used as part of the name
of the file used to create the lock in the local filesystem. A best practice for Symfony commands
is to use the command name, such as ``acme:my-command``. ``LockHandler`` sanitizes the
contents of the string before creating the file, so you can pass any value for this argument.
```