Dashboard code cleanup (#13996)

* Dashboard Cleanup
Remove static widgets table, list of available widgets should not be in the database.
Remove legacy ajax scripts
Cleanup and reorganize controllers

* reorganize code to put all dashboard things into it's controller
better url scheme while supporting the original

* lint clean ups

* properly formatted language file

* style fixes

* update schema

database/seeders/DatabaseSeeder.php

@@ -14,7 +14,6 @@ class DatabaseSeeder extends Seeder
     public function run()
     {
         $this->call(DefaultAlertTemplateSeeder::class);
-        $this->call(DefaultWidgetSeeder::class);
         $this->call(DefaultLegacySchemaSeeder::class);
         $this->call(ConfigSeeder::class);
     }