Chatbox extension

I've integrated the opensource YShout ajax chatbox in Shimmie.
I've e-mailed the author to request permission to use this shoutbox on my website as well as in every other website using Shimmie and I was granted permission.

Currently it comes with only one theme and theres a few other things that need to be finished, which is why the title of the block is Chatbox (Beta).
But it should be ready for use without additional configuration.

I'll also try to integrate the features of the YShout control panel into the Shimmie config panel later on.