Foreign key tests are skipped due to Jenkins' sqlite packages

[EliAndrewC]

Moved here from the (now private) original Sideboard issue tracker.

We currently have two tests for foreign key support where we make sure that deleting a row (especially over our CRUD API) cascades. This works on my machine but fails on some other machines, and some basic Googling shows that foreign key support is not always compiled into SQLite. Depending on your package your foreign key declarations in your CREATE TABLE statements may just be ignored in SQLite.

We should do two things:

• confirm whether that's true before doing any work on this ticket, since I didn't spend enough time to be certain of what I was reading
• detect whether SQLite has foreign key support compiled in, and only skip() if it isn't via the skipif decorator