Revised and updated Tutorials.

- added pictures shown during the tutorials belonging to the text.
- shortened and updated texts.
- sorted the tutorial levels to be more topic related.
- tutorial1 and 2 merged to new tutorial1.
- new mission for new tutorial1.
- old Tutorial1 still avaiable as Tutold1 in 3dbe version.
- new graphics for tutorial 1, 2, 3 and 5.