PHP code style proposal

Readable version: https://github.com/tristanlins/contao-standards-recommendation/blob/propose/php-code-style/proposed/csr-x-php-code-style.md
I do not agree here. IMO the visibility is most important.
This is emphased even more as statics can also be called non static and when ever you want to use a static, you already know it is static from the nature of the function as it will perform some task unrelated to an instance or even return an internally created instance.
Therefore, for `abstract` and `final` I am on your side, for static I am not.