[For 1.8] MyConversations: a conversation plugin for MyBB

[HLFadmin]

At this time, after almost 4 years use in my forum, I see that the message author and admin should be able to edit. Ability to edit to "Message deleted" is sufficient to retain numbering. Admin should have the ability to delete a conversation, although making it a soft delete might be a better way. Delete capability is lower priority than edit capability.

Essentially, a conversation is like a forum thread, just directed to named participants. As we use it.

I will support any effort to add editing capability to Conversations.