[Console] Added a cookbook entry on invoking other commands

This is a follow-up to an issue I've opened in [symfony/symfony](https://github.com/symfony/symfony/issues/12495). It describes how to find and execute other commands from a Symfony `Command`.
I find it a bit misleading the use of the `name` argument name, because all the other names and values are synthetic (`foo`, `bar`, `foobar`). Moreover, using `name` may make some developers think that you should pass the name of the comment as the first argument. Should we change it for some `foo / bar` related word?