Restructure the module lifecycle.

Install: <module>_installer::install() is called, any necessary tables
are created.

Activate: <module>_installer::activate() is called.  Module
controllers are routable, helpers are accessible, etc.  The module is
in use.

Deactivate: <module>_installer::deactivate() is called.  Module code
is not accessible or routable.  Module is *not* in use, but its tables
are still around.

Uninstall: <module>_installer::uninstall() is called.  Module is
completely removed from the database.

Admin > Modules will install and activate modules, but will only
deactivate (will NOT uninstall modules).

modules/comment/helpers/comment_installer.php

@@ -61,6 +61,5 @@ class comment_installer {
     module::event("item_related_update_batch", $sql);
 
     $db->query("DROP TABLE IF EXISTS {comments};");
-    module::delete("comment");
   }
 }