Release of first version of part on axiomatic characterization

This constitutes the final slides stack used for recording the part on the axiomatic characterization of stable models.

Videos of this part part can be found at the urls listed in VIDEO.md.

Most of the LaTeX source of this release can be found at https://github.com/potassco-asp-course/axiomatic-characterization
included as a submodule in https://github.com/potassco-asp-course/course