Xkeywords

@gauteh  Can you take a look at this for me?  I am trying to add full X-Keywords synchronization for better interoperability with Gmail.  I think I am getting the headers set right, but I'm having trouble with writing the changed Maildir file back to the file system.  You don't need to merge this, I just wanted you to see where I was going and ask if you could give me a pointer to where I should be rewriting the file.  In addition, do I need to somehow update the index before or after writing?  Thanks.