Merge branch 'fourthContainer_extension' into 'master'.

This merge will introduce the forth container interface extension to the code.
The Tutorial (Jupyter notebooks) where modified to accommodate for that.
The exercises where also slightly modified.
I have also added the final presentation of the project.
Beside that several small fixes and improvements were done, see the commit log for more details.
This is probably the last commit for a long time.

The best way to start from here is to read the manual and the Jupyter tutorials and solving the final test.
If you speak German, there is also an “Übergabe-Protokoll”, it contains some highlights and gives further hints where to start digging.

Sincerely, Philip Müller