Make test-project working fodlder, introducing doc

Now the test-project folder is a working directory. This means that the
project you are currently working on always lies inside test-project. If
you want to change what you are working on, change the contents of
test-project. This will make it easier to work on both nin and another
project at the same time.

All example code has been moved into a doc folder. This folder is
intended to be a catalog with effects and so on. If you want to add an
effect we might use, please add it to the doc folder.