Expressive 3 upgrade

[asgrim]

• [x] Use psr/http-server-middleware directly
• [x] DelegateInterface => RequestHandlerInterface
• [x] $delegate->process => $requestHandler->handle
• [x] Conceptual rename "actions" => "handlers"
• [x] Created ConfigProvider for app and move relevant config into there
• [x] Rework config.php to use Zend\ConfigAggregator to merge config (uses ConfigProviders much more heavily now)
• [x] Updated pipeline.php to pipe PathBasedRoutingMiddleware and DispatchMiddleware instead of pipeRoutingMiddleware() and pipeDispatchMiddleware()
• [x] Updated index.php, to made pipeline.php and routes.php into invokable functions