Add __repr__ to class AndList

[dimitri-yatsenko]

We added the AndList to handle lists of restrictions in Relation but it lacks a __repr__ method, so our restricted relations now look ugly.

[dimitri-yatsenko]

I am about to close it as a won't fix.

Developing a meaningful __repr__ for relations and their restrictions is a difficult problem that's hard to test and is therefore prone to bugs. Developers have better tools for inspecting objects than the repr.

[dimitri-yatsenko]

addressed in 4debbd8