Sync with Symfony Standard v3.4

[teohhanhui]

Some notable changes:

• Switch to config/services.yml (see Added a new services.yml file to comply with Symfony Best Practices symfony/symfony-standard#727)
• Use autowiring (as per the assumption of https://symfony.com/doc/3.4/service_container.html#service-container-services-load-example)
• Set provider on each firewall (see [SecurityBundle] Deprecate auto picking the first provider symfony/symfony#24378)
• Remove trusted_proxies from config.yml (see https://symfony.com/blog/fixing-the-trusted-proxies-configuration-for-symfony-3-3 and Removed the "trusted_proxies" entry from config.yml symfony/symfony-standard#1060)
• Use single quotes in YAML (see Use single quotes for YAML strings symfony/symfony-docs#5935 and Use single quotes and project_dir parameter symfony/symfony-standard#1065)
• Use %kernel.project_dir% instead of %kernel.root_dir% (see Use single quotes and project_dir parameter symfony/symfony-standard#1065)
• Add some missing declare(strict_types=1);
• Remove author blocks (same as Sylius)

[teohhanhui]

@pamil Any feedback on this?

[pamil]

I'm on it! :)

[pamil]

Btw. can you rebase it to 1.1 branch (it already requires Symfony 3.4)?

[teohhanhui]

Rebased.

[pamil]

The only thing that might cause issues here is "Remove bin-dir in composer.json", mostly with documentation, this PR will be good to merge after it's extracted to master (1.2) branch. Thanks for the effort and patience 🎉

[teohhanhui]

Reverted the changes related to removing bin-dir.

Added some more changes to fix some deprecation messages:

• Set provider on each firewall (see [SecurityBundle] Deprecate auto picking the first provider symfony/symfony#24378)
• Remove trusted_proxies from config.yml (see https://symfony.com/blog/fixing-the-trusted-proxies-configuration-for-symfony-3-3 and Removed the "trusted_proxies" entry from config.yml symfony/symfony-standard#1060)

[pamil]

Thanks Teoh! 🎉