[For 1.8] MyConversations: a conversation plugin for MyBB

[Laird]

MyConversations version 1.1.2 has just been released.

This is a minor bugfix release. No security issues are involved.

New features and fixes:

• Bugfix: "MyBB Engine" and "Guest" were sometimes being shown in place of the correct participant names.
  
• Bugfix: A couple of reversions of edits to core templates were sometimes failing on plugin deactivation (those template edits support the display of MyConversations "likes" in the postbit and postbit_classic templates).
  
• Improved template caching (minor).
  
• Minor improvements to the code supporting the ACP migration tools (nothing user-visible).