Flow settings, viewport update mode, new content

Using a new viewport update mode feature you can now make a flow update the views of nodes when they get updated, even if the flow isn't fully finished with the current execution. That's really useful for larger pure data flows doing data processing (like in the OpenCV example, try it there). Furthermore, Flows now have their own settings which get saved and loaded to and from project files to choose an algorithm mode and the new viewport update mode. Also, I added a small 'bubble sort' example and some basic nodes (there are still quite a few missing, though).