Add a filter so that you can hide admin notification

The admin notification "MinQueue helper is currently active" can be pretty annoying.
I propose we add a filter to let theme authors and plugin developers remove this notice from the admin dashboard.

Here is how you would do that with the proposed change, from a plugin or theme:

```php
add_filter('minqueue_disable_helper_notice', function($var) {
	return true;
});
```