Implemented feature: user display-id now automatically inserts into the IRC nickname box

Added the requested feature at https://www.bountysource.com/issues/462439-irc-if-user-is-logged-in-set-username-for-webchat . Additionally, the old functionality for inserting "Guest#####" was kept for users that aren't logged-in.
![exampleirc](https://f.cloud.github.com/assets/2794246/906603/736a7e02-fcbb-11e2-9a5c-56cb810f0ce9.png)