[wp-forums] Note to moderators about Plugin support forums

[Otto]

Okay, after this thread earlier today:
http://wordpress.org/support/topic/twitter-likes-longer-showing-up-on-my-blog?replies=4

I added the ability for moderators to change the plugin that a
particular thread is attached to. You'll find a "Plugin Slug" box over
in the sidebar for plugin threads. Only moderators can see or edit it.

Notes:
- Don't typo the slug, please. :)
- Blanking it out will make it not attached anymore, and also remove
your ability to edit it again because then it's no longer attached to
a plugin at all. I'd recommend not doing that either.

I'll add safety checks to it as needed. You can't actually break
anything, just make it mildly inconvienent for me to correct at the
moment. Use it sparingly and wisely.

-Otto