Proposal for further core refactoring

[Schlaefer]

This is an proposal for a core refactoring. Don't sweat over single lines or methods. This is work in progress but should be concrete enough for general feedback.

• Config handling moves from array into a class
• Event moves away from static usage
• new config/ directory
• new config/bootstrap.php
  • Bootstrap-process isn't hardcoded anymore but configured here. Let advanced users change the bootstrap process.
  • Core provides basic functions to support bootstrap.
• migrate to PSR-7 Request and Response
  • zendframework/zend-diactoros picked as implementation (no strong opinion)
• implements simple PSR-15 middleware runner Core\RequestHanlder
  • allows 3rd-party middleware
  • core Phile\Phile becomes middleware itself
• Nothing was removed, still backwards compatible.

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Update 2018-02-20: adds a Container as global resource provider

• It's a close call. We could still get away without, but imho it will creep up eventually (esp. for the router).
• Should replace Phile\Core\Registry in a future breaking release.
• Lightweight internal implementation/no external implementation. I don't think we need a feature rich but more complex 3rd party library.
• PSR-11 interface if an external solution is ever needed.
• Static access to get instance(?). Should be the only static global object in the future providing access to:
  • event-bus
  • config
  • router
• new config/container.php to configure the Container

Should still be fully backwards compatible.

[Schlaefer]

Closed in favor of #317