Enabled the PHP CS rule to fix the file header comment

[javiereguiluz]

To avoid issues like #510.

[javiereguiluz]

Now the tests fail because the PHP files in app/ and web/ don't have this header. We won't add it to those files, so how can we solve this?

[apetitpa]

Add ->notPath('web/app_dev.php') etc to $finder in .php_cs file ? But this would exclude those files from other checks. I don't know if this is something acceptable.

[javiereguiluz]

Yes ... but we want the rest of the rules applied to app/ and web/ files :(

[apetitpa]

I don't think there is a way to exclude some checks for a particular path. Maybe this could be a new feature.

[yceruto]

@javiereguiluz if we let the license be included in these files?

[javiereguiluz]

@yceruto let's do that because I honestly see no other solution.