Move default settings to install step

The various installation "frontends" (such as GUI and console) can now
provide custom overrides, if they want to.

src/Install/Controller/InstallController.php

@@ -80,22 +80,8 @@ class InstallController implements RequestHandlerInterface
                 'email' => array_get($input, 'adminEmail'),
             ])
             ->settings([
-                'allow_post_editing' => 'reply',
-                'allow_renaming' => '10',
-                'allow_sign_up' => '1',
-                'custom_less' => '',
-                'default_locale' => 'en',
-                'default_route' => '/all',
-                'extensions_enabled' => '[]',
                 'forum_title' => array_get($input, 'forumTitle'),
-                'forum_description' => '',
-                'mail_driver' => 'mail',
                 'mail_from' => 'noreply@'.preg_replace('/^www\./i', '', parse_url($baseUrl, PHP_URL_HOST)),
-                'theme_colored_header' => '0',
-                'theme_dark_mode' => '0',
-                'theme_primary_color' => '#4D698E',
-                'theme_secondary_color' => '#4D698E',
-                'welcome_message' => 'This is beta software and you should not use it in production.',
                 'welcome_title' => 'Welcome to '.array_get($input, 'forumTitle'),
             ])
             ->build();