Add ACP setting for last post quote

Especially in recent years and with new users there is always the problem that the last post of a topic is quoted in full (especially if quick-reply is not enabled).

This also happens with posts that are inside the topic but here we can't do anything about it, another matter. I wrote an extension for that already.

The problem as I've said has been shown to be massive with the last post of a conversation, we have clear examples on the main site as well. Leaving intact the possibility to quote in full a post in topic-review I think adding an option is the right thing to do.

I know there are extensions for this but I think it should be offered natively: exclude QUOTE from the last post if the admin thinks it is necessary.

I offer to write the PR if I find that this proposal will be well received.