Implement simple python classes (according to sec. 2.1.1 in the overleaf Py2EO Mapping document)

[dours]

[dours]

Partially implemented in https://github.com/polystat/py2eo/tree/hackCage . It is currently blocked by objectionary/eo#508 (a test with a while loop cannot compile because of this problem) . Fixing objectionary/eo#512 instead of 508 may also help, but I think that fixing objectionary/eo#508 is easier.

[dours]

first version is implemented in #68

[0pdd]

@dours the puzzle #402 is still not solved.