Flowlayout

Add a FlowLayout control.

This is not perfect yet, I think we need to figure out more about what we want in terms of GUI stuff. However, it should work reasonably well for the specific case of the infobar.

Let me know if there is stuff that you need in this, I can add it before merging the pull request (or you can add it if you want to and need the functionality right away).

This includes changes that add an additional bar to the right, which just serves as a demo. Try it out, and let me know what you think. I'll remove the demo before actually merging.