Support for status messages

By posting messages with type BubbleTypeMyStatus or BubbleTypeSomeoneElsesStatus plain text messages without a bubble or avatar can be presented.

These are useful to display misc information like "The user left the chat" etc.

![img_2766](https://f.cloud.github.com/assets/442007/578853/bb404a68-c863-11e2-8cc1-5e660234aef6.png)