Update to Laravel 5.7 (PHP 7.3 support) (#9800)

* Move assets to 5.7 location

* Add 5.7 SVGs

* add cache data dir

* update QUEUE_DRIVER -> QUEUE_CONNECTION

* Update trusted proxy config

* update composer.json

* 5.5 command loading

* @php and @endphp can't be inline

* Laravel 5.6 logging, Nice!

* Update blade directives

* improved redirects

* remove unneeded service providers

* Improved debugbar loading

* no need to emulate renderable exceptions anymore

* merge updated 5.7 files (WIP)

* Enable CSRF

* database_path() call causes issue in init.php

* fix old testcase name

* generic phpunit 7 fixes

* add missed file_get_contents
Keep migrations table content

* fix duplicate key

* Drop old php versions from travis-ci

* remove hhvm

* fix code climate message

* remove use of deprecated function assertInternalType

* Disable CSRF, we'll enable it separately.
All forms need to be updated to work.

* Update document references

webpack.mix.js

@@ -1,4 +1,4 @@
-let mix = require('laravel-mix');
+const mix = require('laravel-mix');
 
 /*
  |--------------------------------------------------------------------------
@@ -11,5 +11,5 @@ let mix = require('laravel-mix');
  |
  */
 
-mix.js('resources/assets/js/app.js', 'public/js')
-   .sass('resources/assets/sass/app.scss', 'public/css');
+mix.js('resources/js/app.js', 'public/js')
+   .sass('resources/sass/app.scss', 'public/css');