add irc links if included in metadata - not ready for merge

This implements #1235, adding an IRC link using metadata, mibbit, or freenode's web client.

I think a web client is much friendlier than an irc:// link for the type of users this is trying to reach, but it may be good to present the raw link as well.

I'd prefer to get comments from the people on the issue before merging this.