Start creating tests for the new Bongard domain

[amahabal]

Keep adding tests, so that we know that the code there works (although we cannot of course test that the documentation that goes with it produces that code...).

I should also get into the habit of running tests before submitting. I just did, and a Seqsee test broke sometime in the last two days, that I cannot fix today.

[amahabal]

The failing test has now been fixed. A class had been deleted accidentally in a prior change (in farg/apps/seqsee/codelet_families/all.py).