[Twig] Add trans and transchoice tag support

[Haehnchen]

In PhpStorm8 we are able to provide completion for trans and transchoice tags now.

http://symfony.com/doc/current/book/translation.html#twig-templates

{% trans with {'%name%': 'Fabien'} from "app" %}Hello %name%{% endtrans %}

{% trans with {'%name%': 'Fabien'} from "app" into "fr" %}Hello %name%{% endtrans %}

{% transchoice count with {'%name%': 'Fabien'} from "app" %}
    {0} %name%, there are no apples|{1} %name%, there is one apple|]1,Inf] %name%, there are %count% apples
{% endtranschoice %}