Moved utf8mb4 migration to command instead of migration

To prevent errors upon migration.
Command generates out the SQL syntax to make the change instead
so the upgrade can be done manually.

In reference to #425

app/Console/Kernel.php

@@ -15,7 +15,8 @@ class Kernel extends ConsoleKernel
         Commands\ClearActivity::class,
         Commands\ClearRevisions::class,
         Commands\RegeneratePermissions::class,
-        Commands\RegenerateSearch::class
+        Commands\RegenerateSearch::class,
+        Commands\UpgradeDatabaseEncoding::class
     ];
 
     /**