minor #927 Fixed transitive dependencies usage (javiereguiluz)

This PR was squashed before being merged into the master branch (closes #927).

Discussion
----------

Fixed transitive dependencies usage

I was playing with the "transitive dependencies usage" inspection and lots of errors were reported. Our code uses some classes that belong to packages not required explicitly in our `composer.json`.

For example, we have lots of console commands with lots of `use Symfony\Component\Console\...` import but we never required `symfony/console` ... so it worked thanks to some package requiring symfony/console indirectly.

Same happens to lots of other missing dependencies. However, should we add all of them?

* These seem obvious to me that we should add them: Console, Intl, OptionsResolver.
* These could be added or not: Twig (added indirectly by TwigBundle), all the security/* micro-dependencies (added indirectly by SecurityBundle), EventDispatcher, Doctrine Common, Doctrine Persistence, etc.
* I think we should not add these: HttpFoundation, HttpKernel, Routing, etc.

What do you think?

Commits
-------

f17a647 Fixed transitive dependencies usage

Author: javiereguiluz

composer.json

@@ -14,10 +14,12 @@
         "sensio/framework-extra-bundle": "^5.1",
         "sensiolabs/security-checker": "^5.0",
         "symfony/asset": "*",
+        "symfony/console": "*",
         "symfony/expression-language": "*",
         "symfony/flex": "^1.1",
         "symfony/form": "*",
         "symfony/framework-bundle": "*",
+        "symfony/intl": "*",
         "symfony/monolog-bundle": "^3.1",
         "symfony/polyfill-php72": "^1.8",
         "symfony/security-bundle": "*",
@@ -28,6 +30,7 @@
         "symfony/webpack-encore-bundle": "dev-master",
         "symfony/yaml": "*",
         "twig/extensions": "^1.5",
+        "twig/twig": "^2.6",
         "white-october/pagerfanta-bundle": "^1.1"
     },
     "require-dev": {