Add support for normal pagination.

[ShindouMihou]

While working on migrating Amelia from its own custom command system to Velen, I encountered one issue with pagination and that is, the fact that the current pagination method doesn't support normal pagination where you don't have a select reaction.

As always, my idea for this pagination is simple:

new Paginate<String>(results).paginateSimple(event, new PaginateSimpleEvent<>() {...});

The method: paginateSimple would simply be paginate but without the select reaction which means, there will only be three reactions: cancel, next and back.