[Console] The interactive shell is deprecated

[xabbuh]

The interactive shell will be deprecated in Symfony 2.8 (see symfony/symfony#15892) and we should reflect the fact in the documentation (it is described in the cookbook).

[Tobion]

Code Removed in symfony/symfony#15936

[xabbuh]

@Tobion and I talked about this and we thought that it could be a good idea to remove the documentation for this feature in older branches too.

@javiereguiluz @weaverryan @wouterj What do you think?

[wouterj]

Afaik, our normal plan with deprecations is to show a big caution box before the description of a deprecated feature in older versions and only remove it in the 3.0 version. I think we should do the same here.

[javiereguiluz]

I agree with @wouterj.

[weaverryan]

This is already merged :)