Add ECS and apply standard sets

[TomasVotruba]

• replace cs fixer with ecs
• update compose run
• [cs] apply PSR-12 and other sets

[TomasVotruba]

As request yesterday :)

I see the php-cs-fixer now requires PHP 7.3, which is a pitty. ECS solves this 👍

I've applied all typical comon sets, including PSR 12 and strict types. I think the code is now sooo much better quality 💪
Let me know if there is something you really don't like.

Otherwise it's ready to go 👍

[staabm]

Looks great. 🙏

[TomasVotruba]

Awesome 👍

[staabm]

btw: I have also running a green PHP 7.2 CI job.