Master file is now in HTML instead of Word

* The master for all tutorials/worksheets is now in HTML instead of Word. The HTML is on the code.makery.ch website. The converted worksheets can still be downloaded as Word files from that website.
* Remove Word and PowerPoint files from GitHub repository.
* Change numbering of scenarios/tasks. Now we have 1.01 for the first scenario of chapter one, 1.02 for the second scenario, etc.