add doctrine/coding-standard

[connorhu]

This is an alternative reality of #112

When I was working on the beberlei/DoctrineExtensions repo I came across the doctrine code standard rules package. This is a much more extensive set of rules than can be done with php-cs-fixer (I can understand why they work with this instead of php-cs-fixer). After the commit in the PR there are still about 4000 bugs that need to be fixed manually. I'm sure I missed all the changes causing breaking changes, but at first glance it looks like this. Since doctrine uses it, I think it might be more appropriate to use it in this repo.

[alquerci]

IMHO, coding standard is bound to a team not on repository.

All repositories should use the same rules across FriendsOfSymfony1 organization.

[connorhu]

We also have to take into account that the codebase must retain its characteristics. If we had created all the code from the beginning, I would agree with the principle of "the same everywhere" code style, but we are trying to keep code from different places alive (not develop it, because apparently nobody wants that).

[connorhu]

errors are gone :)
All in all, I prefer this solution because it has more features than the fixer, it has a better reporting system and therefore it is easier to see on github what the problem is.