New message display

I'm implementing a new message display. At the end it should looking like the mockup. The work is still in progress but I would like to present the current state.

![screenshot](http://s7.directupload.net/images/130822/868zd7mr.png)

On this state it is only a replacement for the old one. The only new feature is emoticon support. I added some smileys from fatcows icon set, which can easily replaced later.

As I said, work in progress. You can always find the current state on https://github.com/Schlumpf/ProjectTox-Qt-GUI/tree/message-display till the next pull request.