Add missing autoload include for console components page

And better explain where files should be placed in order to be auto-loaded.
Hmm, all great points!

When I was updating some component docs the other day, it *did* occur to me that we're leaving out the detail of requiring the autoloader (so making the docs not really copy-pastable). So *that* does seem like a small detail we could add to help people. For example, if you look at the Finder component, we would just need to add the `require` for the `autoload.php` in the first code block and maybe just a few others http://symfony.com/doc/current/components/finder.html. I'm thinking whenever we show a full example (i.e. include the `use` statement), we could also include the `require` line and a little `// foo.php` filename comment at the top. What do you guys think about this part?

Second, there is this autoloading proposal. The good news is, I don't think this affects most component docs (we don't ever create any objects in the Finder docs, for example). If I do a `git grep "namespace "`, it only shows 7 of the components. For these, I think it might be nice to add a quick note near-ish the first related code example that mentions this autoloader code. So, what do you guys think about *this* part?

Thanks!