Remove unecessary mentions of the ODW edition

[duboism]

Currently, the materials contains some mentions of the year and/or edition of the ODW. As the repository will be used for several years, we should remove such mentions except where necessary (which probably boils down to the README).

[martinberoiz]

Just as a reminder, we'll also have to modify the image and remove the year. It's good that the logo will remain unchanged in future workshops to build the brand.