- BC Break: Upgraded required _PHP_ v7.1 → v7.2

- BC Break: Core _PHP_ framework + dependencies moved into `composer.json` and are no longer part of this repo
- Upgraded some 3rd party _Composer_ dependencies: `monolog/monolog`, `swiftmailer/swiftmailer`, `league/html-to-markdown`, `react/socket`, `react/promise-stream`
- Fixed a bug where `/setup` throws HTTP `5xx` error if no `pathfinder` DB exists
- Fixed compatibility issue with PHP `v7.4`, closed #887

app/main/controller/controller.php

@@ -132,7 +132,7 @@ class Controller {
             $f3->get('SESSION_CACHE') === 'mysql' &&
             ($db = $f3->DB->getDB('PF')) instanceof SQL
         ){
-            if(!headers_sent() && session_status()!=PHP_SESSION_ACTIVE){
+            if(!headers_sent() && session_status() != PHP_SESSION_ACTIVE){
                 /**
                  * callback() for suspect sessions
                  * @param $session