User interface testing

To test if our rendering engine is robust enough and check to see what kind of
user interface is good to create, this week I'm working on testing a user
interface. I decided to draw buttons on the right hand side as it looks nice
and needs less changes on the engine code. Each view has now got a text to
indicate which view it is. I think we should have a status bar at the bottom
of the knot rendering area. Three buttons are drawn for the testing: Select,
Add points, and Delete.