hook_imagecache_default_presets_alter() to modify another module's presets

Like Views has hook_views_default_views_alter(), it would be useful to have hook_imagecache_default_presets_alter() to be able to modify another module's presets during load. This would allow us to modify an existing module's presets in code without leaving changes exclusively in the database, which isn't good for deployment / reusability purposes.